US20090136854A1

US20090136854A1 - Lithium Ion Secondary Battery

Info

Publication number: US20090136854A1
Application number: US11/887,320
Authority: US
Inventors: Kensuke Nakura
Original assignee: Individual
Current assignee: Panasonic Corp
Priority date: 2005-07-07
Filing date: 2006-06-26
Publication date: 2009-05-28
Also published as: KR101068282B1; JP5085856B2; US20110033756A1; CN101203970A; JP2007018874A; KR20070116919A; CN100559638C; WO2007007541A1

Abstract

The present invention intends to improve the intermittent cycle characteristics in a lithium ion secondary battery including, as a positive electrode active material, a lithium composite oxide mainly composed of nickel or cobalt. The present invention is a lithium ion secondary battery wherein the positive electrode includes active material particles including a lithium composite oxide. The lithium composite oxide is represented by the general formula (1): Li_xM_1-yL_yO₂(where 0.85≦x≦1.25, 0≦y≦0.50, and element M is at least one selected from the group consisting of Ni and Co, and element L is at least one selected from the group consisting of alkaline earth elements, transition metal elements, rare earth elements, Group IIIb elements and Group IVb elements). The surface layer of the active material particles includes element Le being at least one selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W and Y. The active material particles are surface-treated with a coupling agent.

Description

TECHNICAL FIELD

The present invention relates to a lithium ion secondary battery with excellent life characteristics.

BACKGROUND ART

Lithium secondary batteries typical of non-aqueous electrolyte secondary batteries have high electromotive force and high energy density. Because of these features, lithium secondary batteries are now in increasing demand as a main power supply of mobile communication devices and portable electronic devices.
Enhancing reliability of lithium ion secondary batteries has been a crucial technical challenge in development thereof. A lithium composite oxide such as Li_xCoO₂or Li_xNiO₂(where x varies depending on charging and discharging of a battery) includes Co⁴⁺ or Ni⁴⁺ with a high valence, which has an excellent reactivity during charging. Because of this, under a high temperature environment, decomposition reaction of electrolyte correlated with a lithium composite oxide is facilitated, and gas is generated in the battery, making it impossible to obtain sufficient cycle characteristics and high temperature storage characteristics.
In order to suppress reaction between an active material and an electrolyte of lithium ion secondary batteries, one proposal suggests that the surface of a positive electrode active material be treated with a coupling agent (Patent Documents 1 to 3). A stable coating film is formed on the surface of active material particles by virtue of the coupling agent, whereby the electrolyte decomposition reaction correlated with a lithium composite oxide is suppressed.
In view of suppressing the reaction between an active material and an electrolyte to improve cycle characteristics and high temperature storage characteristics, and other points, another proposal suggests that various elements be added to the positive electrode active material (Patent Documents 4 to 8).
With respect to Li_xNiO₂, improving water resistance has been a challenge. In light of this, there has been proposed that the surface of Li_xNiO₂be rendered hydrophobic with a coupling agent to improve the stability of the active material (Patent Document 9).

Patent Document 1: Japanese Laid-Open Patent Publication Hei 11-354101

Patent Document 2: Japanese Laid-Open Patent Publication 2002-367610

Patent Document 3: Japanese Laid-Open Patent Publication Hei 8-111243

Patent Document 4: Japanese Laid-Open Patent Publication Hei 11-16566

Patent Document 5: Japanese Laid-Open Patent Publication 2001-196063

Patent Document 6: Japanese Laid-Open Patent Publication Hei 7-176302

Patent Document 7: Japanese Laid-Open Patent Publication Hei 11-40154

Patent Document 8: Japanese Laid-Open Patent Publication 2004-111076

Patent Document 9: Japanese Laid-Open Patent Publication 2000-281354

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

As described above, many proposals have been made in order to suppress gas generation and improve cycle characteristics and high temperature storage characteristics. However, these techniques have points to be improved as follows.
Many of lithium ion secondary batteries are used in various portable devices. The various portable devices are not always used immediately after the batteries are charged. In many cases, the batteries are left in a charged state for a long period of time and thereafter discharged. The current situation is, however, that the cycle life characteristics of the batteries are generally evaluated under conditions different from such actual conditions for use as described above.
For example, a typical cycle life test is performed under a condition with a short rest (pause) time after charging (for example, rest time: 30 min). In the case where evaluation is performed under such a condition, the cycle life characteristics can be improved to some extent with the above technologies as have been conventionally suggested.
However, assuming the actual conditions for use, in the case where an intermittent cycle (charge and discharge cycle with a long rest time after charging) is repeated, favorable results about the cycle life characteristics have not yet been obtained. For example, it has been found that in the case of a cycle life test with a rest time of 720 minutes, neither one of the above described technologies can provide sufficient life characteristics. In other words, a remaining challenge with respect to the conventional lithium ion secondary batteries is to improve intermittent cycle characteristics.

Means for Solving the Problem

In view of the above, the present invention intends to improve intermittent cycle characteristics in a lithium ion secondary battery including a lithium composite oxide containing nickel or cobalt as the positive electrode active material.
Specifically, the present invention relates to a lithium ion secondary battery having a chargeable and dischargeable positive electrode, a chargeable and dischargeable negative electrode, and a non-aqueous electrolyte, wherein the positive electrode includes active material particles, the active material particles include a lithium composite oxide, the lithium composite oxide is represented by the general formula (I): Li_xM_1-yL_yO₂, the general formula (1) satisfies 0.85≦x≦1.25 and 0≦y≦0.50, element M is at least one selected from the group consisting of Ni and Co, element L is at least one selected from the group consisting of alkaline earth elements, transition metal elements, rare earth elements, Group IIIb elements and Group IVb elements, the surface layer of the active material particles includes element Le being at least one selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W and Y, and the active material particles are surface-treated with a coupling agent.
It is preferable that in the general formula (I), when 0<y, element L includes at least one selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W and Y as an essential element.
It is preferable that the silane coupling agent forms a silicon compound bonded to the surface of the active material particles through Si—O bonds as a result of the surface treatment.
In one general embodiment of the present invention, element L and element Le form crystalline structures different from each other. For example, element Le forms an oxide or a lithium-containing oxide having a crystalline structure different from that of the lithium composite oxide.
The amount of the coupling agent is preferably less than or equal to 2 wt % relative to the active material particles.
In the present invention, various silane coupling agents may be used. It is desirable that the silane coupling agent includes at least one selected from the group consisting of an alkoxide group and a chlorine atom, and at least one selected from the group consisting of a mercapto group, an alkyl group and a fluorine atom.
The mean particle size of the active material particles is preferably more than or equal to 10 μm.
In view of achieving further improvement in intermittent cycle characteristics, it is preferable that the non-aqueous electrolyte includes at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, phosphazene and fluorobenzene.

EFFECTS OF THE INVENTION

According to the present invention, it is possible to improve intermittent cycle characteristics than ever before in a lithium ion secondary battery including a lithium composite oxide mainly composed of nickel or cobalt (Ni/Co based Li composite oxide) as a positive electrode active material. As for the reason why the intermittent cycle characteristics can be secured, only a phenomenological reason is recognized at present.
It should be noted that simply surface treating active material particles containing a Ni/Co based Li composite oxide with a coupling agent provides only a slight improvement in intermittent cycle characteristics. Similarly, simply including element Le in the surface layer of the active material particles provides only a slight improvement in intermittent cycle characteristics.
However, including element Le in the surface layer of active material particles containing a Ni/Co based Li composite oxide plus surface-treating the active material particles with a coupling agent provides a drastic improvement in intermittent cycle characteristics. This has been confirmed by various experiments.
It is considered that the drastic improvement in intermittent cycle characteristics has relevance to that the peeling-off of the coupling agent is suppressed. The coupling agent is bonded to oxygen present in the surface of the active material particles. It is considered that in the case where element Le is not present in the surface layer of the active material particles, oxygen being bonded to the coupling agent is separated from the active material surface during intermittent cycles. As a result, it is considered that the coupling agent loses a function of suppressing the decomposition reaction of electrolyte.
On the other hand, it is considered that in the case where element Le is present in the surface layer of the active material particles, oxygen is not readily separated from the active material surface because of increased dissociation energy of oxygen. It is considered that this suppresses the peeling off of the coupling agent from the active material surface during intermittent cycles, allowing the function of the coupling agent to be maintained.
It is difficult at present to accurately analyze what form element Le may take in the surface layer of the active material particles. However, it can be confirmed by various methods that element Le is carried on at least part of the surface of the Ni/Co based Li composite oxide, and present in a state of an oxide or a lithium-containing oxide having a crystalline structure different from that of the Ni/Co based Li composite oxide. These methods include element mapping by EPMA (Electron Probe Micro-Analysis), analysis of chemical bonding state by XPS (X-ray Photoelectron Spectroscopy), analysis of surface composition by SIMS (Secondary Ionization Mass Spectroscopy) and the like.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 A vertical sectional view of a cylindrical lithium ion secondary battery according to Example of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A positive electrode according to the present invention will be hereinafter described. The positive electrode includes active material particles as follows.
The active material particles include a lithium composite oxide mainly composed of nickel or cobalt (Ni/Co based Li composite oxide). Although the form of the lithium composite oxide is not particularly limited, for example, there are cases where the lithium composite oxide is in a state of primary particles and forms the active material particles and where the lithium composite oxide is in a state of secondary particles and forms the active material particles. A plurality of the active material particles may be aggregated to form secondary particles.
Although, a mean particle size of the active material particles or the Ni/Co based Li composite oxide particles is not particularly limited, for example, preferred is 1 to 30 μm, and particularly preferred is 10 to 30 μm. The mean particle size may be measured with a wet laser diffraction type particle size distribution meter manufactured by MICRO TRUCK CO., LTD. In this case, the volume basis 50% value (median value: D₅₀) can be regarded as the mean particle size.
The lithium composite oxide is represented by the general formula (I): Li_xM_1-yL_yO₂. The general formula (I) satisfies 0.85≦x≦1.25 and 0≦y≦0.50. Element M is at least one selected from the group consisting of Ni and Co. Element L is at least one selected from the group consisting of alkaline earth elements, transition metal elements, rare earth elements, Group IIIb elements and Group IVb elements. Element L provides the lithium composite oxide with effects of improving thermal stability and the like.
It is preferable that in the general formula (I), when 0<y, the lithium composite oxide preferably includes at least one selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W and Y as element L. These elements may be included in the lithium composite oxide singly or may be included in combination of two or more as element L. Among these, Al is preferred as element L because of its strong bonding strength with oxygen. Further, Mn, Ti and Nb are preferred. Although Ca, Sr, Si, Sn, B, etc. may be included as element L, using these in combination with Al, Mn, Ti, Nb, etc. is desired.
The range of x representing a Li content is increased or decreased in association with charge and discharge of a battery. The range of x in a full discharge state (initial state) may be 0.85≦x≦1.25; however, preferred is 0.93≦x≦1.1.
The range of y representing an element L content may be 0≦y≦0.50; however, preferred is 0≦y≦0.50 and particularly preferred is 0.001≦y≦0.35 in light of the balance among the capacity, the cycle characteristics, the thermal stability and the like.
In the case where element L includes Al, the atomic ratio a of Al to the total of Ni, Co and element L is preferably 0.005≦a≦0.1, and particularly preferably 0.01≦a≦0.08.
In the case where element L includes Mn, the atomic ratio b of Mn to the total of Ni, Co and element L is preferably 0.005≦b≦0.5, and particularly preferably 0.01≦b≦0.35.
In the case where element L includes at least one selected from the group consisting of Ti and Nb, the atomic ratio c of Ti and/or Nb to the total of Ni, Co and element L is preferably 0.001≦c≦0.1, and particularly preferably 0.001≦c≦0.08.
The lithium composite oxide represented by the above-described the general formula may be synthesized by baking a starting material having a predetermined metallic element ratio in an oxidizing atmosphere. In the starting material, lithium, nickel (and/or cobalt) and element L are included. The starting material includes an oxide, a hydroxide, an oxyhydroxide, a carbonate, a nitrate, an organic complex salt or the like of each metallic element. These may be used singly or in combination of two or more.
In light of facilitating synthesis of the lithium composite oxide, it is preferable that the starting material includes a solid solution containing a plurality of metallic elements. The solid solution containing a plurality of metallic elements can be formed in any form such as an oxide, a hydroxide, an oxyhydroxide, a carbonate, a nitrate or an organic complex salt. For example, it is preferable to use a solid solution containing Ni and Co, a solid solution containing Ni and element L, a solid solution containing Co and element L, a solid solution containing Ni, Co and element L or the like.
Although the baking temperature of the starting material and the oxygen partial pressure in the oxidizing atmosphere are dependent on the composition of the starting material, the amount of the starting material, synthesizing apparatus and the like, one skilled in the art would select appropriate conditions, as needed.
There may be a case where elements other than Li, Ni, Co and element L get mixed as impurities in an amount within a range in which they are normally included in an industrial starting material; however, this will not significantly affect the effects of the present invention.
The surface layer of the active material particles according to the present invention includes element Le. Herein, element Le is at least one selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W and Y. The surface layer of the active material particles may include these elements singly or in an optional combination of two or more. The surface layer of the active material particles may contain other elements such as alkaline earth elements, transition metal elements, rare earth elements, Group IIIb elements and Group IVb elements as optional components.
It is preferable that element Le is in a state of an oxide or a lithium-containing oxide, and is deposited, attached or carried on the surface of the lithium composite oxide.
Element L dissolved in the lithium composite oxide and element Le included in the surface layer of the active material particles may or may not contain an element of the same kind. When element L and element Le contain an element of the same kind, these are clearly distinguishable from each other because the crystalline structures etc. thereof are different. Element Le is not dissolved in the lithium composite oxide, but mainly forms an oxide having a crystalline structure different from that of the lithium composite oxide in the surface layer of the active material particles. Element L and element Le are distinguishable by various analytic methods exemplified by EPMA, XPS and SIMS.
Although the range of an atomic ratio z of element Le to the total of Ni, Co and element L contained in the active material particle is not particularly limited, preferred is 0.001≦z≦0.05, and particularly preferred is 0.001≦z≦0.01. When z is too small, the effect of suppressing the peeling-off of a coupling agent during intermittent cycles is not obtained sufficiently. On the other hand, when z is too great, since the surface layer of the active material particles functions as a resistant layer to increase the overvoltage, the intermittent cycle characteristics start to degrade.
There may be a case where element Le in the surface layer is dispersed in the lithium composite oxide, and the concentration of element L in the lithium composite oxide becomes higher in the vicinity of the surface layer than in the interior of the active material particles. Namely, there may be a case where element Le in the surface layer is transformed into element L forming the lithium composite oxide.
Element L originated from element Le having been dispersed in the lithium composite oxide is present in the vicinity of the surface layer, and presumably acts similarly to element Le. However, the amount of element Le dispersed in the lithium composite oxide is as small as negligible, which hardly affects the effects of the present invention.
The lithium composite oxide forming the active material particles may be primary particles or secondary particles formed by aggregation of a plurality of primary particles. Alternatively, a plurality of the active material particles may be aggregated to form secondary particles.
Preferred as a source material of element Le included in the surface layer of the active material particles are a sulfate, a nitrate, a carbonate, a chloride, a hydroxide, an oxide, an alkoxide and the like. These may be used singly or in combination of two or more. Among these, particularly preferred is a sulfate, a nitrate, a chloride or an alkoxide in light of battery performance.
The surface of the active material particles is surface-treated with a coupling agent.
The coupling agent has at least one organic functional group and a plurality of bonding groups in its molecule. The organic functional group has various hydrocarbon skeletons. The bonding groups give hydroxyl groups each directly bonded to a metallic atom (for example, Si—OH, Ti—OH or Al—OH) through hydrolysis. A silane coupling agent has in its molecular, for example, an organic functional group such as an alkyl group, a mercaptopropyl group or a trifluoropropyl group, and bonding groups such as alkoxy groups or chlorine atoms that give silanol groups (Si—OH) through hydrolysis.
The “treating with a coupling agent” as used herein means to allow hydroxyl groups (OH groups) present in the surface of the active material particles or the lithium composite oxide to react with the bonding groups in the coupling agent. For example, when the bonding groups are alkoxy groups (OR groups: R=alkyl group), alcohol dissociation reaction proceeds between the alkoxy groups and the hydroxyl groups; and when the bonding groups are chlorine atoms (Cl atoms), the elimination reaction of hydrogen chloride (HCl) proceeds between the chlorine atoms and the hydroxyl groups.
Whether treated with a coupling agent or not can be confirmed by the formation of X—O—Si bond (where X is the surface of the active material particles or the lithium composite oxide), X—O—Ti bond, X—O—Al bond or the like. When the lithium composite oxide includes Si, Ti, Al, etc. as element L, the Si, Ti and Al forming the lithium composite oxide are distinguishable from the Si, Ti and Al originated from the coupling agent because of the difference in structure.
Usable as the coupling agent are, for example, a silane coupling agent, an aluminate based coupling agent and titanate based coupling agent. These may be used singly or in combination of two or more. Among these, it is preferable to use a silane coupling agent in view of its capabilities of coating the surface of the active material particles with an inorganic polymer having a skeleton of siloxane bonds, and suppressing side reaction. Namely, it is preferable that the active material particles carry a silicon compound as a result of the surface treatment.
Considering the reactivity with the hydroxyl groups in the surface of the active material particles, it is preferable that the silane coupling agent has at least one selected from the group consisting of an alkoxy group and a chlorine atom as the bonding group. Moreover, in view of suppressing side reaction with the electrolyte, it is preferable that the silane coupling agent has at least one selected from the group consisting of a mercapto group, an alkyl group and a fluorine atom.
The amount of the coupling agent to be added to the active material particles is preferably less than or equal to 2 wt % relative to the active material particles, and more preferably 0.05 to 1.5 wt %. When the adding amount of the coupling agent exceeds 2 wt %, the surface of the active material is excessively coated with the coupling agent that does not contribute to the reaction, and consequently the cycle characteristics may be degraded.
Next, an example of a method of producing the positive electrode will be described.

(i) First Step

A lithium composite oxide represented by the general formula (I): Li_xM_1-yL_yO₂is prepared. The method of preparing the lithium composite oxide is not particularly limited. For example, the lithium composite oxide may be synthesized by baking a starting material having a predetermined metallic element ratio in an oxidizing atmosphere. The baking temperature, the oxygen partial pressure in the oxidizing atmosphere and the like are selected as needed, depending on the composition of the starting material, the amount of the starting material, synthesizing apparatus, etc.

(ii) Second Step

The lithium composite oxide thus prepared is allowed to carry a source material of element Le (at least one selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W and Y). In this case, although the mean particle size of the lithium composite oxide is not particularly limited, 1 to 30 μm is preferred. Value z (the atomic ratio of element Le to the total of Ni, Co and element L) can be usually determined from the amount of element Le contained in the source material used in this step relative to that of the lithium composite oxide.
For the source material of element Le, a sulfate, a nitrate, a carbonate, a chloride, a hydroxide, an oxide, an alkoxide and the like including element Le are used. These may be used singly or in combination of two or more. Among these it is particularly preferable to use a sulfate, a nitrate, a chloride or an alkoxide in light of battery performance. The method of allowing the source material of element Le to be carried on the lithium composite oxide is not particularly limited. For example, it is preferable to dissolve or disperse the source material of element Le in a liquid component to prepare solution or dispersion, subsequently mix the solution or the dispersion with the lithium composite oxide, and then remove the liquid component.
Although the liquid component in which the source material of element Le is dissolved or dispersed is not particularly limited, ketones such as acetone, methyl ethyl ketone (MEK), ethers such as tetrahydrofuran (THF), alcohols such as ethanol, and other organic solvents are preferred. Alkaline water of pH 10 to 14 may be preferably used.
When introducing the lithium composite oxide to the solution or the dispersion thus obtained and stirring it, the temperature of the solution or the dispersion is not particularly limited. However, in view of workability and production costs, the temperature is preferably controlled to 20 to 40° C. Although the stirring time is not particularly limited, stirring for as long as 3 hours, for example, is satisfactory. Although the method of removing the liquid component is not particularly limited, drying at a temperature of approximately 100° C. for about 2 hours, for example, is satisfactory.
(iii) Third Step
The lithium composite oxide carrying element Le on the surface thereof is baked at 650 to 750° C. for 2 to 24 hours, preferably approximately 6 hours under an oxygen atmosphere. Herein, the pressure of the oxygen atmosphere is preferably 101 to 50 KPa. By this baking, element Le is transformed into an oxide having a crystalline structure different from that of the lithium composite oxide.

(iv) Fourth Step

The active material particles thus obtained are surface-treated with a coupling agent. The method of surface-treating is not particularly limited. For example, the coupling agent is merely added to the active material particles. However, in view of diffusing the coupling agent through the whole active material particles, adding the coupling agent to a positive electrode material mixture paste is desirable. For example, a positive electrode material mixture including the active material particles, a conductive agent and a binder is dispersed in a liquid component to prepare a positive electrode material mixture paste, and then a coupling agent is added thereto, followed by stirring it.
Although the liquid component into which the positive electrode material mixture is dispersed is not particularly limited, ketones such as acetone, methyl ethyl ketone (MEK), ethers such as tetrahydrofuran (THF), alcohols such as ethanol, N-methyl-2-pyrrolidone (NMP) and the like are preferred. Alkaline water of pH 10 to 14 may be preferably used.
The temperature of the paste during stirring after the coupling agent is introduced thereto is preferably controlled to 20 to 40° C. Although the stirring time is not particularly limited, stirring for as long as 15 minutes, for example, is satisfactory.
The positive electrode material mixture paste thus obtained is applied onto a positive electrode core material (positive electrode current collector) and then dried, whereby a positive electrode including active material particles surface-treated with a coupling agent is obtained. Although the drying temperature and time after the paste is applied onto the positive electrode core material are not particularly limited, drying at a temperature of approximately 100° C. for about 10 minutes, for example, is satisfactory.
For the binder to be included in the positive electrode material mixture, either one of a thermoplastic resin and a thermosetting resin may be used; however, a thermoplastic resin is preferred. Examples of the thermoplastic resin include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoro methyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, and ethylene-methyl methacrylate copolymer. These may be used singly or in combination of two or more. These may be a crosslinked product by Na ions etc.
The conductive material to be included in the positive electrode material mixture may be any one as long as it is an electron conductive material that is chemically stable in a battery. For example, graphite such as natural graphite (scale-shaped graphite etc.) and artificial graphite; carbon blacks such as acetylene black, Ketjen Black, channel black, furnace black, lampblack, and thermal black; conductive fibers such as carbon fibers and metal fibers; powders of metal such as aluminum; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; organic conductive materials such as polyphenylene derivatives; and fluorinated carbons and the like may be used. These may be used singly or in combination of two or more. Although the adding amount of the conductive material is not particularly limited, preferred is 1 to 50 wt % relative to the active material particles included in the positive electrode material mixture, more preferred is 1 to 30 wt % and particularly preferred is 2 to 15 wt %.
The positive electrode core material (positive electrode current collector) may be any one as long as it is an electron conductive material that is chemically stable in a battery. For example, foil or sheet made of aluminum, stainless steel, nickel, titanium, carbon, a conductive resin or the like may be used. In particular, aluminum foil, aluminum alloy foil or the like is preferred. On the surface of the foil or sheet, a layer of carbon or titanium may be provided or an oxide layer may be formed. In addition, the surface of the foil or sheet may be made rough. A net, a punched sheet, a lath, a porous material, a foam, a molded article formed by fiber bundle or the like may also be used. Although the thickness of the positive electrode core material is not particularly limited, for example, it is within a range of 1 to 500 μm.
Other components other than the positive electrode of the lithium ion secondary battery of the present invention will be hereinafter described. However, since the lithium ion secondary battery of the present invention has its feature in that it includes the positive electrode as described above, no particular limitation is imposed on other components. Therefore, the present invention is not limited by the following description.
For the lithium chargeable and dischargeable negative electrode, for example, one that comprises a negative electrode core material carrying a negative electrode material mixture including a negative electrode active material and a binder and optionally including a conductive material and a thickening agent may be used. Such a negative electrode may be fabricated in the same manner as in the positive electrode.
The negative electrode active material may be a material capable of electrochemically charging and discharging lithium. For example, graphite, non-graphitizable carbon materials, lithium alloys, metal oxides or the like may be used. Particularly preferred among lithium alloys is an alloy containing at least one selected from the group consisting of silicon, tin, aluminum, zinc and magnesium. Preferred among metal oxides are an oxide containing silicon and an oxide containing tin, which are more preferred if hybridized with a carbon material. Although the mean particle size of the negative electrode active material is not particularly limited, to 30 μm is preferred.
For the binder to be included in the negative electrode material mixture, either one of a thermoplastic resin and a thermosetting resin may be used; however, a thermoplastic resin is preferred. Examples of the thermoplastic resin include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoro methyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, and ethylene-methyl methacrylate copolymer. These may be used singly or in combination of two or more. These may be a crosslinked product by Na ions etc.
The conductive material to be included in the negative electrode material mixture may be any material as long as it is an electron conductive material that is chemically stable in a battery. Examples of the conductive material include graphite such as natural graphite (scale-shaped graphite etc.) and artificial graphite, carbon blacks such as acetylene black, Ketjen Black, channel black, furnace black, lampblack, and thermal black; conductive fibers such as carbon fibers and metal fibers; powders of metal such as cupper or nickel; and organic conductive materials such as polyphenylene derivatives. These may be used singly or in combination of two or more. Although the adding amount of the conductive material is not particularly limited, preferred is 1 to 30 wt %, and more preferred is 1 to 10 wt % relative to the active material particles included in the negative electrode material mixture.
The negative electrode core material (negative electrode current collector) may be any one as long as it is an electron conductive material that is chemically stable in a battery. For example, foil or sheet made of stainless steel, nickel, cupper, titanium, carbon, a conductive resin or the like may be used. In particular, cupper or a cupper alloy is preferred. On the surface of the foil or sheet, a layer of carbon, titanium, nickel, etc. may be provided or an oxide layer may be formed. In addition, the surface of the foil or sheet may be made rough. A net, a punched sheet, a lath, a porous material, a foam, a molded article formed by fiber bundle or the like may also be used. Although the thickness of the negative electrode core material is not particularly limited, for example, it is within a range of 1 to 500 μm.
For the non-aqueous electrolyte, a non-aqueous solvent with a lithium salt dissolved therein is preferably used.
Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate (BC); chain carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC); aliphatic carboxylic acid esters such as methyl formate, methyl acetate, methyl propionate and ethyl propionate; lactones such as γ-butyrolactone and γ-valerolactone; chain esters such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE) and ethoxymethoxyethane (EME); cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; dimethylsulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethyl ether, 1,3-propane sultone, anisole, dimethylsulfoxide and N-methyl-2-pyrrolidone. These may be used singly or in combination of two or more. Preferred among these is a mixture solvent of a cyclic carbonate and a chain carbonate, or a mixture solvent of a cyclic carbonate, a chain carbonate and an aliphatic carboxylic acid ester.
Examples of the lithium salt to be dissolved in the non-aqueous solvent include LiClO₄, LiBF₄, LiPF₆, LiAlCl₄, LiSbF₆, LiSCN, LiCl, LiCF₃SO₃, LiCF₃CO₂, Li(CF₃SO₂)₂, LiAsF₆, LiN(CF₃SO₂)₂, LiB₁₀Cl₁₀, lithium lower aliphatic carboxylate, LiCl, LiBr, LiI, chloroborane lithium, lithium tetraphenylborate and lithium imide salts. These may be used singly or in combination of two or more; however, it is preferable to use at least LiPF₆. Although the dissolving amount of the lithium salt in the non-aqueous solvent is not particularly limited, the concentration of lithium salt is preferably 0.2 to 2 mol/L and more preferably 0.5 to 1.5 mol/L.
To the non-aqueous electrolyte, various additives may be added for the purpose of improving charge and discharge characteristics of a battery. Examples of the additives include triethyl phosphate, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, pyridine, hexaphosphoric triamide, nitrobenzene derivatives, crown esters, quaternary ammonium salts and ethylene glycol dialkyl ether.
In view of improving intermittent cycle characteristics, it is preferable that at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, phosphazene and fluorobenzene is added to the non-aqueous electrolyte. An appropriate content of these additives is 0.5 to 10 wt % relative to the non-aqueous electrolyte.
It is necessary to interpose a separator between the positive electrode and the negative electrode.
For the separator, an electrically-insulating microporous thin film having high ion permeability and a predetermined mechanical strength is preferably used. It is preferable that the microporous thin film has a function that closes pores at a predetermined temperature or higher to increase resistance. As a material for the microporous thin film, a polyolefin such as polypropylene or polyethylene being excellent in resistance to organic solvent and having hydrophobicity is preferably used. Sheet, nonwoven fabric or woven fabric made of glass fibers or the like is also used. The pore size of the separator is, for example, 0.01 to 1 μm. The thickness of the separator is typically 10 to 300 μm. The porosity of the separator is typically 30 to 80%.
A polymer electrolyte comprising a non-aqueous electrolyte and a polymer material holding the same may be used as the separator in combination with the positive electrode or the negative electrode. The polymer material may be any material as long as it can retain the non-aqueous electrolyte; however, a copolymer of vinylidene fluoride and hexafluoropropylene is particularly preferred.
Next, the present invention will be specifically described with reference to Examples; however, the present invention is not limited to the following Examples.

EXAMPLE 1

Battery 1A-2

(1) Synthesis of Lithium Composite Oxide

Nickel sulfate, cobalt sulfate and aluminum sulfate were mixed so that the molar ratio of Ni atom, Co atom and Al atom was 80:15:5. To 10 L of water, 3.2 kg of the mixture thus obtained was dissolved to prepare a starting material solution. To the starting material solution, 400 g of sodium hydroxide was added to form a precipitate. The precipitate was washed with water sufficiently, and then dried to yield a coprecipitated hydroxide.
To 3 kg of the Ni—Co—Al coprecipitated hydroxide thus obtained, 784 g of lithium hydroxide was added and mixed, and then the mixture was baked for 10 hours at a synthesizing temperature of 750° C. in an atmosphere with an oxygen partial pressure of 0.5 atm. As a result, a Ni/Co based Li composite oxide containing Al as element L (LiNi_0.8CO_0.15Al_0.05O₂) was obtained.

(2) Synthesis of Active Material Particles

<i> First Step
Into a solution of niobium chloride dissolved in 10 L of ethanol, 2 kg of the lithium composite oxide thus synthesized was dispersed. The amount of the niobium chloride used was 0.5 mol % relative to the lithium composite oxide (namely, 0.5 mol % relative to the total of Ni, Co and Al). The ethanol solution with the lithium composite oxide dispersed therein was stirred at 25° C. for 3 hours. Thereafter the solution was filtered and a solid matter obtained by filtration was dried at 100° C. for 2 hours. As a result, a lithium composite oxide carrying niobium (Nb) on the surface thereof as element Le was obtained.
<ii> Second Step
The powder after drying was subjected to pre-baking at 300° C. for 6 hours under a dry air atmosphere (humidity: 19%, pressure: 101 KPa).
Subsequently, the powder after pre-baking was subjected to final baking at 650° C. for 6 hours under an oxygen 100% atmosphere (pressure: 101 KPa).
Finally, the powder after final baking was annealed at 400° C. for 4 hours under an oxygen 100% atmosphere (pressure: 101 KPa).
As a result of this baking, active material particles comprising a lithium composite oxide and a surface layer containing Nb were obtained. The presence of Nb in the surface layer was confirmed by XPS, EPMA, ICP emission spectrometry or the like. In the following Examples, the presence of element Le in the active material particles was similarly confirmed by XPS, EPMA, ICP emission spectrometry or the like. In the following Examples, the presence of element Le in the surface layer of the active material particles was similarly confirmed by XPS, EPMA, ICP emission spectrometry or the like.

(3) Fabrication of Positive Electrode

A positive electrode material mixture paste was prepared by stirring 1 kg of the active material particles thus obtained (mean particle size: 12 μm) together with 0.5 kg of PVDF #1320 (N-methyl-2-pyrrolidone (NMP) solution with a solid content of 12 wt %) manufactured by KUREHA CORPORATION, 40 g of acetylene black, 10 g of 3-mercaptopropyltrimethoxysilane (silane coupling agent: KBM-803 manufactured by Shin-Etsu Chemical Co., Ltd.) and an appropriate amount of NMP at 30° C. for 30 minutes with a double arm kneader. This paste was applied onto both faces of a 20 μm thick aluminum foil (positive electrode core material), subsequently dried at 120° C. for 15 minutes, and then rolled until the total thickness reached 160 μm. Thereafter, the electrode plate thus obtained was slit into a width that could be inserted into a cylindrical battery case of size 18650, whereby a positive electrode was obtained.

(4) Fabrication of Negative Electrode

A negative electrode material mixture paste was prepared by stirring 3 kg of artificial graphite together with 200 g of BM-400B manufactured by ZEON Corporation (dispersion of modified styrene-butadiene rubber with a solid content of 40 wt %), 50 g of carboxymethyl cellulose (CMC) and a proper amount of water with a double arm kneader. This paste was applied onto both faces of a 12 μm thick copper foil (negative electrode core material), subsequently dried, and then rolled until the total thickness reached 160 μm. Thereafter, the electrode plate thus obtained was slit into a width that could be inserted into a cylindrical battery case size 18650, whereby a negative electrode was obtained.

(5) Preparation of Non-Aqueous Electrolyte

In a mixture solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 10:30, 2 wt % vinylene carbonate, 2 wt % vinylethylene carbonate, 5 wt % fluorobenzene and 5 wt % phosphazene were added. In the solution thus obtained, LiPF₆was dissolved at a concentration of 1.5 mol/L, whereby a non-aqueous electrolyte was obtained.

(6) Assembly of Battery

As shown in FIG. 1, a positive electrode 5 and a negative electrode 6 were wound with a separator 7 interposed therebetween to give a spiral-shaped electrode assembly. For the separator 7, composite film of polyethylene and polypropylene (2300 manufactured by Celgard Inc., thickness: 25 μm) was used.
To the positive electrode 5 and the negative electrode 6, a positive electrode lead 5 a and a negative electrode lead 6 a made of nickel were attached, respectively. An upper insulating plate 8 a and a lower insulating plate 8 b were disposed on the upper face and the lower face of this electrode assembly, respectively, and then the whole was inserted into a battery case 1. Subsequently, 5 g of non-aqueous electrolyte was injected into the battery case 1.
Thereafter, a sealing plate 2 with a sealing gasket 3 disposed on the circumference thereof was brought into electrical conduction with the positive electrode lead 5 a, and then the opening of the battery case 1 was sealed with the sealing plate 2. In such a manner, a cylindrical lithium ion secondary battery of size 18650 was obtained. This is referred to as Example Battery 1A-2.

Battery 1A-1

As Comparative Example, Battery 1A-1 was fabricated in the same manner as in Battery 1A-2 except that Nb was not carried as element Le on the Ni/Co based Li composite oxide.

Battery 1A-3

Battery 1A-3 was fabricated in the same manner as in Battery 1A-2 except that the amount of the niobium chloride to be dissolved in 10 L of ethanol was changed to 1.0 mol % relative to the Ni/Co based Li composite oxide (namely, 1.0 mol % relative to the total of Ni, Co and Al).

Battery 1A-4

In place of the ethanol solution of niobium chloride, 2 kg of Ni/Co based Li composite oxide was dispersed in 1 L of pH 13 aqueous sodium hydroxide solution. In the dispersion thus obtained, an aqueous solution of 0.5 mol % manganese (Mn) sulfate relative to the Ni/Co based Li composite oxide dissolved in 100 g of distilled water was dropped for the duration of 10 minutes, and then stirred at 100° C. for 3 hours. Battery 1A-4 was fabricated in the same manner as in Battery 1A-2 except the above.

Battery 1A-5

Battery 1A-5 was fabricated in the same manner as in Battery 1A-4 except that the amount of the manganese sulfate to be dissolved in 100 g of distilled water was changed to 1.0 mol % relative to the Ni/Co based Li composite oxide.

Battery 1A-6

In place of the ethanol solution of niobium chloride, 2 kg of Ni/Co based Li composite oxide was dispersed in 1 L of pH 13 aqueous sodium hydroxide solution. In the dispersion thus obtained, an aqueous solution of 0.5 mol % titanium (Ti) nitrate relative to the Ni/Co based Li composite oxide dissolved in 100 g of distilled water was dropped for the duration of 10 minutes, and then stirred at 100° C. for 3 hours. Battery 1A-6 was fabricated in the same manner as in Battery except the above.

Battery 1A-7

Battery 1A-7 was fabricated in the same manner as in Battery 1A-6 except that the amount of the titanium nitrate to be dissolved in 100 g of distilled water was changed to 1.0 mol % relative to the Ni/Co based Li composite oxide.

Battery 1A-8

In place of the ethanol solution of niobium chloride, 2 kg of Ni/Co based Li composite oxide was dispersed in 1 L of pH 13 aqueous sodium hydroxide solution. In the dispersion thus obtained, an aqueous solution of 0.5 mol % magnesium (Mg) acetate relative to the Ni/Co based Li composite oxide dissolved in 100 g of distilled water was dropped for the duration of 10 minutes, and then stirred at 100° C. for 3 hours. Battery 1A-8 was fabricated in the same manner as in Battery 1A-2 except the above.

Battery 1A-9

Battery 1A-9 was fabricated in the same manner as in Battery 1A-8 except that the amount of the magnesium acetate to be dissolved in 100 g of distilled water was changed to 1.0 mol % relative to the Ni/Co based Li composite oxide.

Battery 1A-10

In 10 L of butanol, 0.5 mol % zirconium (Zr) tetra-n-butoxide relative to the Ni/Co based Li composite oxide was dissolved. Battery 1A-10 was fabricated in the same manner as in Battery 1A-2 except that the solution thus obtained was used in place of the ethanol solution of niobium chloride.

Battery 1A-11

Battery 1A-11 was fabricated in the same manner as in Battery 1A-10 except that the amount of the zirconium tetra-n-butoxide to be dissolved in 10 L of butanol was changed to 1.0 mol % relative to the Ni/Co based Li composite oxide.

Battery 1A-12

In 10 L of isopropanol, 0.5 mol % aluminum (Al) triisopropoxide relative to the Ni/Co based Li composite oxide was dissolved. Battery 1A-12 was fabricated in the same manner as in Battery 1A-2 except that the solution thus obtained was used in place of the ethanol solution of niobium chloride.

Battery 1A-13

Battery 1A-13 was fabricated in the same manner as in Battery 1A-12 except that the amount of the aluminum triisopropoxide to be dissolved in 10 L of isopropanol was changed to 1.0 mol % relative to the Ni/Co based Li composite oxide.

Battery 1A-14

In place of the ethanol solution of niobium chloride, 2 kg of Ni/Co based Li composite oxide was dispersed in 1 L of pH 13 aqueous sodium hydroxide solution. In the dispersion thus obtained, an aqueous solution of 0.5 mol % disodium molybdate (Mo) dihydrate relative to the Ni/Co based Li composite oxide dissolved in 100 g of distilled water was dropped for the duration of 10 minutes, and then stirred at 100° C. for 3 hours. Battery 1A-14 was fabricated in the same manner as in Battery 1A-2 except the above.

Battery 1A-15

Battery 1A-15 was fabricated in the same manner as in Battery 1A-14 except that the amount of the disodium molybdate dihydrate to be dissolved in 100 g of distilled water was changed to 1.0 mol relative to the Ni/Co based Li composite oxide.

Battery 1A-16

In place of the ethanol solution of niobium chloride, 2 kg of Ni/Co based Li composite oxide was dispersed in 1 L of pH 13 aqueous sodium hydroxide solution. In the dispersion thus obtained, an aqueous solution of 0.5 mol % sodium tungstate (W) relative to the Ni/Co based Li composite oxide dissolved in 100 g of distilled water was dropped for the duration of 10 minutes, and then stirred at 100° C. for 3 hours. Battery 1A-16 was fabricated in the same manner as in Battery 1A-2 except the above.

Battery 1A-17

Battery 1A-17 was fabricated in the same manner as in Battery 1A-16 except that the amount of the sodium tungstate to be dissolved in 100 g of distilled water was changed to 1.0 mol % relative to the Ni/Co based Li composite oxide.

Battery 1A-18

In place of the ethanol solution of niobium chloride, 2 kg of Ni/Co based Li composite oxide was dispersed in 1 L of pH 13 aqueous sodium hydroxide solution. In the dispersion thus obtained, an aqueous solution of 0.5 mol % yttrium (Y) nitrate relative to the Ni/Co based Li composite oxide dissolved in 100 g of distilled water was dropped for the duration of 10 minutes, and then stirred at 100° C. for 3 hours. Battery 1A-18 was fabricated in the same manner as in Battery 1A-2 except the above.

Battery 1A-19

Battery 1A-19 was fabricated in the same manner as in Battery 1A-18 except that the amount of the yttrium nitrate to be dissolved in 100 g of distilled water was changed to 1.0 mol % relative to the Ni/Co based Li composite oxide.

Battery 1A-21

Battery 1A-21 was fabricated in the same manner as in Battery 1A-1 except that the amount of 3-mercaptopropyltrimethoxysilane (silane coupling agent) to be added to the positive electrode material mixture paste was changed to 25 g per 1 kg of active material particles.

Batteries 1A-22 to 1A-39

Batteries 1A-22 to 1A-39 were fabricated in the same manner as in Batteries 1A-2 to 1A-19 except that the amount of 3-mercaptopropyltrimethoxysilane (silane coupling agent) to be added to the positive electrode material mixture paste was changed to 25 g per 1 kg of active material particles.

Evaluation 1

Intermittent Cycle Characteristics

Each battery was subjected to preliminary charge and discharge twice, and then stored for two days under an environment of 40° C. Thereafter, each battery was subjected to repeated cycles of the following two patterns. The design capacity of the battery was 1 CmAh.

First Pattern (Normal Cycle Test)

(1) Constant current charge (45° C.): 0.7 CmA (cut-off voltage 4.2 V)
(2) Constant voltage charge (45° C.): 4.2 V (cut-off current 0.05 CmA)
(3) Charge rest (45° C.): 30 min
(4) Constant current discharge (45° C.): 1 CmA (cut-off voltage 3V)
(5) Discharge rest (45° C.): 30 min

The Second Pattern (Intermittent Cycle-Test)

(1) Constant current charge (45° C.): 0.7 CmA (cut-off voltage 4.2 V)
(2) Constant voltage charge (45° C.): 4.2 V (cut-off current 0.05 CmA)
(3) Charge rest (45° C.): 720 min
(4) Constant current discharge (45° C.): 1 CmA (cut-off voltage 3 V)
(5) Discharge rest (45° C.): 720 min
The discharge capacities after 500 cycles obtained in the first and second patterns are show in Table 1A.

TABLE 1A

Lithium composite oxide: LiNi_0.80Co_0.15Al_0.05O₂

		Intermittent cycle
		characteristics
		Capacity after 500
		cycles
Coupling agent	Element Le	Charge rest

	Adding	Adding	30 min	720 min
Battery	amount	amount	at 45° C.	at 45° C.
No.	(wt %)	(mol %)	(mAh)	(mAh)

1A	1	3-mercapto-	1.0	Nil	—	2182	720
	2	propyl-		Nb	0.5	2180	2100
	3	trimethoxy-			1.0	2005	1992
	4	silane		Mn	0.5	2185	2105
	5				1.0	2002	1990
	6			Ti	0.5	2182	2100
	7				1.0	2004	1994
	8			Mg	0.5	2184	2110
	9				1.0	2005	1992
	10			Zr	0.5	2185	2105
	11				1.0	2002	1994
	12			Al	0.5	2180	2107
	13				1.0	2005	1995
	14			Mo	0.5	2180	2108
	15				1.0	2004	1992
	16			W	0.5	2180	2109
	17				1.0	2000	1990
	18			Y	0.5	2182	2110
	19				1.0	2005	1992
	21		2.5	Nil	—	1900	700
	22			Nb	0.5	1900	1805
	23				1.0	1805	1700
	24			Mn	0.5	1905	1802
	25				1.0	1800	1702
	26			Ti	0.5	1902	1804
	27				1.0	1802	1705
	28			Mg	0.5	1905	1805
	29				1.0	1805	1700
	30			Zr	0.5	1904	1800
	31				1.0	1804	1705
	32			Al	0.5	1902	1802
	33				1.0	1802	1702
	34			Mo	0.5	1905	1803
	35				1.0	1804	1700
	36			W	0.5	1904	1804
	37				1.0	1805	1702
	38			Y	0.5	1902	1805
	39				1.0	1802	1705

Batteries 1B-1 to 1B-39

Batteries 1B-1 to 1B-39 were fabricated in the same manner as in Batteries 1A-1 to 1A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to hexyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 1B.

TABLE 1B

Lithium composite oxide: LiNi_0.80Co_0.15Al_0.05O₂

1B	1	Hexyl-	1.0	Nil	—	2180	802
	2	trimethoxy-		Nb	0.5	2175	2110
	3	silane			1.0	2002	1990
	4			Mn	0.5	2174	2108
	5				1.0	2002	1985
	6			Ti	0.5	2176	2105
	7				1.0	2000	1992
	8			Mg	0.5	2177	2108
	9				1.0	2000	1990
	10			Zr	0.5	2177	2107
	11				1.0	2004	1990
	12			Al	0.5	2175	2108
	13				1.0	2003	1985
	14			Mo	0.5	2178	2109
	15				1.0	2000	1992
	16			W	0.5	2177	2110
	17				1.0	2002	1990
	18			Y	0.5	2175	2110
	19				1.0	2004	1992
	21		2.5	Nil	—	1905	702
	22			Nb	0.5	1902	1800
	23				1.0	1800	1705
	24			Mn	0.5	1900	1800
	25				1.0	1802	1702
	26			Ti	0.5	1902	1802
	27				1.0	1800	1704
	28			Mg	0.5	1900	1802
	29				1.0	1802	1702
	30			Zr	0.5	1902	1802
	31				1.0	1805	1700
	32			Al	0.5	1905	1805
	33				1.0	1804	1700
	34			Mo	0.5	1902	1805
	35				1.0	1804	1702
	36			W	0.5	1900	1802
	37				1.0	1802	1704
	38			Y	0.5	1900	1802
	39				1.0	1800	1700

Batteries 1C-1 to 1C-39

Batteries 1C-1 to 1C-39 were fabricated in the same manner as in Batteries 1A-1 to 1A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3-methacryloxypropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 1C.

TABLE 1C

Lithium composite oxide: LiNi_0.80Co_0.15Al_0.05O₂

		Intermittent cycle
		characteristics
		Capacity after 500
	Element	cycles
Coupling agent	Le	Charge rest

1C	1	3-	1.0	Nil	—	2180	805
	2	methacryloxy-		Nb	0.5	2182	2102
	3	propyl-			1.0	2005	1992
	4	trimethoxy-		Mn	0.5	2180	2105
	5	silane			1.0	2000	1990
	6			Ti	0.5	2185	2100
	7				1.0	2002	1991
	8			Mg	0.5	2184	2100
	9				1.0	2002	1994
	10			Zr	0.5	2180	2105
	11				1.0	2004	1995
	12			Al	0.5	2182	2105
	13				1.0	2005	1992
	14			Mo	0.5	2180	2102
	15				1.0	2005	1992
	16			W	0.5	2180	2104
	17				1.0	2004	1995
	18			Y	0.5	2182	2105
	19				1.0	2002	1994
	21		2.5	Nil	—	1902	700
	22			Nb	0.5	1900	1810
	23				1.0	1802	1700
	24			Mn	0.5	1905	1812
	25				1.0	1800	1705
	26			Ti	0.5	1902	1815
	27				1.0	1805	1702
	28			Mg	0.5	1904	1812
	29				1.0	1804	1700
	30			Zr	0.5	1900	1810
	31				1.0	1804	1700
	32			Al	0.5	1901	1810
	33				1.0	1802	1700
	34			Mo	0.5	1901	1810
	35				1.0	1802	1702
	36			W	0.5	1900	1812
	37				1.0	1802	1700
	38			Y	0.5	1900	1815
	39				1.0	1800	1700

Batteries 1D-1 to 1D-39

Batteries 1D-1 to 1D-39 were fabricated in the same manner as in Batteries 1A-1 to 1A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3,3,3-trifluoropropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 1D.

TABLE 1D

Lithium composite oxide: LiNi_0.80Co_0.15Al_0.05O₂

1D	1	3,3,3-	1.0	Nil	—	2178	705
	2	trifluoro-		Nb	0.5	2179	2097
	3	propyl-			1.0	1997	1987
	4	trimethoxy-		Mn	0.5	2180	2099
	5	silane			1.0	1995	1988
	6			Ti	0.5	2177	2098
	7				1.0	1995	1985
	8			Mg	0.5	2178	2099
	9				1.0	1992	1984
	10			Zr	0.5	2177	2097
	11				1.0	1992	1987
	12			Al	0.5	2177	2097
	13				1.0	1995	1985
	14			Mo	0.5	2178	2097
	15				1.0	1995	1988
	16			W	0.5	2177	2097
	17				1.0	1997	1988
	18			Y	0.5	2178	2097
	19				1.0	1997	1989
	21		2.5	Nil	—	1902	699
	22			Nb	0.5	1900	1810
	23				1.0	1802	1700
	24			Mn	0.5	1905	1812
	25				1.0	1800	1705
	26			Ti	0.5	1902	1815
	27				1.0	1805	1702
	28			Mg	0.5	1904	1812
	29				1.0	1804	1700
	30			Zr	0.5	1900	1810
	31				1.0	1804	1700
	32			Al	0.5	1901	1810
	33				1.0	1802	1700
	34			Mo	0.5	1901	1810
	35				1.0	1802	1702
	36			W	0.5	1900	1812
	37				1.0	1802	1700
	38			Y	0.5	1900	1815
	39				1.0	1800	1700

Batteries 1E-1 to 1E-39

Batteries 1E-1 to 1E-39 were fabricated in the same manner as in Batteries 1A-1 to 1A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3,3,4,4,5,5,6,6,6-nonafluorohexyltrichlorosilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 1E.

TABLE 1E

Lithium composite oxide: LiNi_0.80Co_0.15Al_0.05O₂

1E	1	3,3,4,4,5,5,	1.0	Nil	—	2181	812
	2	6,6,6-		Nb	0.5	2182	2105
	3	nonafluoro-			1.0	2002	1995
	4	hexyl-		Mn	0.5	2180	2102
	5	trichloro-			1.0	2000	1992
	6	silane		Ti	0.5	2180	2100
	7				1.0	2002	1990
	8			Mg	0.5	2182	2105
	9				1.0	2004	1990
	10			Zr	0.5	2185	2102
	11				1.0	2002	1989
	12			Al	0.5	2180	2102
	13				1.0	2004	1988
	14			Mo	0.5	2185	2100
	15				1.0	2005	1988
	16			W	0.5	2184	2100
	17				1.0	2004	1988
	18			Y	0.5	2184	2100
	19				1.0	2005	1988
	21		2.5	Nil	—	1905	711
	22			Nb	0.5	1902	1800
	23				1.0	1800	1702
	24			Mn	0.5	1900	1802
	25				1.0	1802	1700
	26			Ti	0.5	1902	1800
	27				1.0	1805	1700
	28			Mg	0.5	1905	1800
	29				1.0	1804	1702
	30			Zr	0.5	1902	1800
	31				1.0	1804	1702
	32			Al	0.5	1900	1800
	33				1.0	1804	1702
	34			Mo	0.5	1900	1802
	35				1.0	1805	1700
	36			W	0.5	1900	1802
	37				1.0	1805	1700
	38			Y	0.5	1902	1802
	39				1.0	1805	1700

Batteries 1F-1 to 1F-39

Batteries 1F-1 to 1F-39 were fabricated in the same manner as in Batteries 1A-1 to 1A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 6-triethoxysilyl-2-norbornene, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 1F.

TABLE 1F

Lithium composite oxide: LiNi_0.80Co_0.15Al_0.05O₂

1F	1	6-triethoxy-	1.0	Nil	—	2190	807
	2	silyl-2-		Nb	0.5	2185	2105
	3	norbornene			1.0	2008	1998
	4			Mn	0.5	2184	2105
	5				1.0	2004	1997
	6			Ti	0.5	2184	2104
	7				1.0	2004	1999
	8			Mg	0.5	2185	2105
	9				1.0	2005	1997
	10			Zr	0.5	2187	2107
	11				1.0	2007	1998
	12			Al	0.5	2187	2107
	13				1.0	2008	1997
	14			Mo	0.5	2188	2108
	15				1.0	2004	1998
	16			W	0.5	2188	2108
	17				1.0	2005	1999
	18			Y	0.5	2187	2108
	19				1.0	2007	1999
	21		2.5	Nil	—	1907	701
	22			Nb	0.5	1910	1808
	23				1.0	1812	1705
	24			Mn	0.5	1908	1807
	25				1.0	1810	1704
	26			Ti	0.5	1907	1807
	27				1.0	1815	1700
	28			Mg	0.5	1908	1805
	29				1.0	1814	1702
	30			Zr	0.5	1909	1807
	31				1.0	1812	1705
	32			Al	0.5	1907	1809
	33				1.0	1810	1704
	34			Mo	0.5	1908	1807
	35				1.0	1815	1705
	36			W	0.5	1909	1808
	37				1.0	1814	1705
	38			Y	0.5	1912	1808
	39				1.0	1815	1704

Batteries 1R-1 to 1R-19

As Comparative Example, Batteries 1R-1 to 1R-19 were fabricated in the same manner as in Batteries 1A-1 to 1A-19 except that the silane coupling agent was not used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 1R.

TABLE 1R

Lithium composite oxide: LiNi_0.80Co_0.15Al_0.05O₂

1R	1	Nil	—	Nil	—	2180	870
	2			Nb	0.5	2180	900
	3				1.0	2005	810
	4			Mn	0.5	2182	902
	5				1.0	2004	815
	6			Ti	0.5	2184	905
	7				1.0	2005	815
	8			Mg	0.5	2182	904
	9				1.0	2004	800
	10			Zr	0.5	2185	905
	11				1.0	2002	815
	12			Al	0.5	2184	904
	13				1.0	2000	812
	14			Mo	0.5	2185	902
	15				1.0	2002	815
	16			W	0.5	2185	902
	17				1.0	2010	812
	18			Y	0.5	2185	900
	19				1.0	2005	810

EXAMPLE 2

Batteries 2A-1 to 2A-39

Nickel sulfate, cobalt sulfate and aluminum sulfate were mixed so that the molar ratio of Ni atom, Co atom and Al atom was 34:33:33. To 10 L of water, 3.2 kg of the mixture thus obtained was dissolved to prepare a starting material solution. To the starting material solution, 400 g of sodium hydroxide was added to form a precipitate. The precipitate was washed with water sufficiently, and then dried to yield a coprecipitated hydroxide.
To 3 kg of the Ni—Co—Al coprecipitated hydroxide thus obtained, 784 g of lithium hydroxide was added and mixed, and then the mixture was baked for 10 hours at a synthesizing temperature of 750° C. in an atmosphere with an oxygen partial pressure of 0.5 atm. As a result, a Ni/Co based Li composite oxide containing Al as element L (LiNi_0.34CO_0.33Al_0.33O₂) was obtained.
Batteries 2A-1 to 2A-39 were fabricated using 3-mercaptopropyltrimethoxysilane in the same manner as in Batteries 1A-1 to 1A-39 of Example 1, respectively, except that the Ni/Co based Li composite oxide thus obtained was used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 2A.

TABLE 2A

Lithium composite oxide: LiNi_0.34Co_0.33Al_0.33O₂

2A	1	3-mercapto-	1.0	Nil	—	1920	802
	2	propyl-		Nb	0.5	1912	1855
	3	trimethoxy-			1.0	1840	1785
	4	silane		Mn	0.5	1915	1858
	5				1.0	1847	1792
	6			Ti	0.5	1914	1876
	7				1.0	1845	1808
	8			Mg	0.5	1915	1877
	9				1.0	1840	1803
	10			Zr	0.5	1911	1873
	11				1.0	1845	1799
	12			Al	0.5	1915	1867
	13				1.0	1844	1798
	14			Mo	0.5	1912	1864
	15				1.0	1846	1791
	16			W	0.5	1911	1854
	17				1.0	1844	1789
	18			Y	0.5	1910	1853
	19				1.0	1845	1790
	21		2.5	Nil	—	1910	700
	22			Nb	0.5	1915	1877
	23				1.0	1847	1810
	24			Mn	0.5	1917	1879
	25				1.0	1840	1803
	26			Ti	0.5	1915	1867
	27				1.0	1842	1796
	28			Mg	0.5	1917	1869
	29				1.0	1844	1798
	30			Zr	0.5	1918	1870
	31				1.0	1847	1792
	32			Al	0.5	1915	1858
	33				1.0	1842	1787
	34			Mo	0.5	1912	1855
	35				1.0	1847	1792
	36			W	0.5	1911	1873
	37				1.0	1845	1808
	38			Y	0.5	1910	1872
	39				1.0	1840	1803

Batteries 2B-1 to 2B-39

Batteries 2B-1 to 2B-39 were fabricated in the same manner as in Batteries 2A-1 to 2A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to hexyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 2B.

TABLE 2B

Lithium composite oxide: LiNi_0.34Co_0.33Al_0.33O₂

2B	1	Hexyl-	1.0	Nil	—	1910	805
	2	trimethoxy-		Nb	0.5	1911	1873
	3	silane			1.0	1850	1813
	4			Mn	0.5	1912	1874
	5				1.0	1855	1809
	6			Ti	0.5	1915	1867
	7				1.0	1854	1808
	8			Mg	0.5	1920	1872
	9				1.0	1852	1796
	10			Zr	0.5	1918	1860
	11				1.0	1857	1801
	12			Al	0.5	1917	1859
	13				1.0	1852	1796
	14			Mo	0.5	1915	1877
	15				1.0	1848	1811
	16			W	0.5	1910	1872
	17				1.0	1846	1809
	18			Y	0.5	1910	1853
	19				1.0	1844	1789
	21		2.5	Nil	—	1900	700
	22			Nb	0.5	1912	1864
	23				1.0	1845	1799
	24			Mn	0.5	1917	1869
	25				1.0	1844	1798
	26			Ti	0.5	1915	1867
	27				1.0	1840	1803
	28			Mg	0.5	1910	1872
	29				1.0	1844	1807
	30			Zr	0.5	1912	1874
	31				1.0	1845	1808
	32			Al	0.5	1917	1869
	33				1.0	1840	1794
	34			Mo	0.5	1911	1863
	35				1.0	1848	1802
	36			W	0.5	1918	1860
	37				1.0	1842	1787
	38			Y	0.5	1919	1861
	39				1.0	1840	1785

Batteries 2C-1 to 2C-39

Batteries 2C-1 to 2C-39 were fabricated in the same manner as in Batteries 2A-1 to 2A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3-methacryloxypropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 2C.

TABLE 2C

Lithium composite oxide: LiNi_0.34Co_0.33Al_0.33O₂

2C	1	3-	1.0	Nil	—	1920	807
	2	methacryloxy-		Nb	0.5	1915	1877
	3	propyl-			1.0	1840	1803
	4	trimethoxy-		Mn	0.5	1900	1862
	5	silane			1.0	1850	1795
	6			Ti	0.5	1910	1853
	7				1.0	1845	1790
	8			Mg	0.5	1920	1862
	9				1.0	1844	1789
	10			Zr	0.5	1915	1858
	11				1.0	1842	1787
	12			Al	0.5	1917	1859
	13				1.0	1846	1800
	14			Mo	0.5	1916	1868
	15				1.0	1841	1795
	16			W	0.5	1918	1870
	17				1.0	1840	1794
	18			Y	0.5	1920	1882
	19				1.0	1845	1808
	21		2.5	Nil	—	1911	698
	22			Nb	0.5	1915	1877
	23				1.0	1845	1790
	24			Mn	0.5	1917	1859
	25				1.0	1840	1785
	26			Ti	0.5	1911	1854
	27				1.0	1842	1796
	28			Mg	0.5	1925	1877
	29				1.0	1844	1798
	30			Zr	0.5	1915	1867
	31				1.0	1843	1788
	32			Al	0.5	1920	1862
	33				1.0	1845	1790
	34			Mo	0.5	1917	1859
	35				1.0	1844	1807
	36			W	0.5	1910	1872
	37				1.0	1840	1803
	38			Y	0.5	1912	1874
	39				1.0	1840	1803

Batteries 2R-1 to 2R-19

As Comparative Example, Batteries 2R-1 to 2R-19 were fabricated in the same manner as in Batteries 2A-1 to 2A-19, respectively, except that the silane coupling agent was not used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 2R.

TABLE 2R

Lithium composite oxide: LiNi_0.34Co_0.33Al_0.33O₂

		Intermittent cycle
		characteristics
Coupling		Capacity after 500 cycles
agent	Element Le	Charge rest

2R	1	Nil	—	Nil	—	1915	712
	2			Nb	0.5	1911	700
	3				1.0	1870	675
	4			Mn	0.5	1915	702
	5				1.0	1872	677
	6			Ti	0.5	1917	704
	7				1.0	1872	678
	8			Mg	0.5	1917	704
	9				1.0	1870	679
	10			Zr	0.5	1910	702
	11				1.0	1877	674
	12			Al	0.5	1912	701
	13				1.0	1874	670
	14			Mo	0.5	1911	708
	15				1.0	1872	672
	16			W	0.5	1915	701
	17				1.0	1871	674
	18			Y	0.5	1917	701
	19				1.0	1871	671

EXAMPLE 3

Batteries 3A-1 to 3A-39

Nickel sulfate, cobalt sulfate and titanium nitrate were mixed so that the molar ratio of Ni atom, Co atom and Ti atom was 80:15:5. To 10 L of water, 3.2 kg of the mixture thus obtained was dissolved to prepare a starting material solution. To the starting material solution, 400 g of sodium hydroxide was added to form a precipitate. The precipitate was washed with water sufficiently, and then dried to yield a coprecipitated hydroxide.
To 3 kg of the Ni—Co—Ti coprecipitated hydroxide thus obtained, 784 g of lithium hydroxide was added and mixed, and then the mixture was baked for 10 hours at a synthesizing temperature of 750° C. in an atmosphere with an oxygen partial pressure of 0.5 atm. As a result, a Ni/Co based Li composite oxide containing Ti as element L (LiNi_0.8CO_0.15Ti_0.05O₂) was obtained.
Batteries 3A-1 to 3A-39 were fabricated using 3-mercaptopropyltrimethoxysilane in the same manner as in Batteries 1A-1 to 1A-39 of Example 1, respectively, except that the Ni/Co based Li composite oxide thus obtained was used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 3A.

TABLE 3A

Lithium composite oxide: LiNi_0.80Co_0.15Ti_0.05O₂

3A	1	3-mercapto-	1.0	Nil	—	2182	812
	2	propyl-		Nb	0.5	2175	2090
	3	trimethoxy-			1.0	1999	1990
	4	silane		Mn	0.5	2175	2095
	5				1.0	2000	1991
	6			Ti	0.5	2174	2092
	7				1.0	2002	1990
	8			Mg	0.5	2172	2095
	9				1.0	2005	1991
	10			Zr	0.5	2170	2094
	11				1.0	2004	1992
	12			Al	0.5	2175	2095
	13				1.0	2000	1995
	14			Mo	0.5	2174	2090
	15				1.0	2004	1994
	16			W	0.5	2175	2095
	17				1.0	2005	1995
	18			Y	0.5	2170	2090
	19				1.0	2000	1995
	21		2.5	Nil	—	1900	689
	22			Nb	0.5	1905	1800
	23				1.0	1800	1720
	24			Mn	0.5	1900	1805
	25				1.0	1802	1722
	26			Ti	0.5	1900	1804
	27				1.0	1802	1720
	28			Mg	0.5	1905	1806
	29				1.0	1802	1727
	30			Zr	0.5	1905	1807
	31				1.0	1800	1727
	32			Al	0.5	1904	1807
	33				1.0	1800	1720
	34			Mo	0.5	1904	1807
	35				1.0	1802	1727
	36			W	0.5	1900	1808
	37				1.0	1805	1728
	38			Y	0.5	1900	1800
	39				1.0	1800	1720

Batteries 3B-1 to 3B-39

Batteries 3B-1 to 3B-39 were fabricated in the same manner as in Batteries 3A-1 to 3A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to hexyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 3B.

TABLE 3B

Lithium composite oxide: LiNi_0.80Co_0.15Ti_0.05O₂

		Intermittent cycle
		characteristics
	Element	Capacity after 500 cycles
Coupling agent	Le	Charge rest

3B	1	Hexyl-	1.0	Nil	—	2180	811
	2	trimethoxy-		Nb	0.5	2175	2080
	3	silane			1.0	2000	1980
	4			Mn	0.5	2175	2079
	5				1.0	2000	1979
	6			Ti	0.5	2174	2078
	7				1.0	2002	1980
	8			Mg	0.5	2174	2080
	9				1.0	2000	1977
	10			Zr	0.5	2170	2080
	11				1.0	2002	1977
	12			Al	0.5	2171	2079
	13				1.0	2004	1977
	14			Mo	0.5	2172	2077
	15				1.0	2002	1987
	16			W	0.5	2172	2077
	17				1.0	2000	1987
	18			Y	0.5	2170	2079
	19				1.0	2000	1987
	21		2.5	Nil	—	1900	698
	22			Nb	0.5	1890	1805
	23				1.0	1800	1700
	24			Mn	0.5	1891	1802
	25				1.0	1799	1700
	26			Ti	0.5	1890	1803
	27				1.0	1797	1702
	28			Mg	0.5	1891	1804
	29				1.0	1799	1705
	30			Zr	0.5	1889	1805
	31				1.0	1799	1704
	32			Al	0.5	1889	1805
	33				1.0	1800	1702
	34			Mo	0.5	1892	1805
	35				1.0	1800	1702
	36			W	0.5	1890	1805
	37				1.0	1800	1703
	38			Y	0.5	1890	1805
	39				1.0	1800	1705

Batteries 3C-1 to 3C-39

Batteries 3C-1 to 3C-39 were fabricated in the same manner as in Batteries 3A-1 to 3A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3-methacryloxypropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 3C.

TABLE 3C

Lithium composite oxide: LiNi_0.80Co_0.15Ti_0.05O₂

3C	1	3-methacry-	1.0	Nil	—	2180	800
	2	loxypropyl-		Nb	0.5	2185	2050
	3	trimethoxy-			1.0	2000	1980
	4	silane		Mn	0.5	2184	2048
	5				1.0	2000	1982
	6			Ti	0.5	2185	2050
	7				1.0	1999	1982
	8			Mg	0.5	2185	2052
	9				1.0	1998	1984
	10			Zr	0.5	2180	2049
	11				1.0	1997	1980
	12			Al	0.5	2185	2048
	13				1.0	2000	1984
	14			Mo	0.5	2180	2050
	15				1.0	2000	1985
	16			W	0.5	2180	2050
	17				1.0	2001	1980
	18			Y	0.5	2180	2052
	19				1.0	1999	1980
	21		2.5	Nil	—	1900	705
	22			Nb	0.5	1905	1810
	23				1.0	1810	1710
	24			Mn	0.5	1900	1808
	25				1.0	1815	1711
	26			Ti	0.5	1905	1804
	27				1.0	1810	1710
	28			Mg	0.5	1900	1805
	29				1.0	1810	1710
	30			Zr	0.5	1900	1807
	31				1.0	1814	1711
	32			Al	0.5	1905	1801
	33				1.0	1812	1710
	34			Mo	0.5	1905	1800
	35				1.0	1813	1711
	36			W	0.5	1905	1805
	37				1.0	1814	1711
	38			Y	0.5	1905	1810
	39				1.0	1815	1711

Batteries 3D-1 to 3D-39

Batteries 3D-1 to 3D-39 were fabricated in the same manner as in Batteries 3A-1 to 3A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3,3,3-trifluoropropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 3D.

TABLE 3D

Lithium composite oxide: LiNi_0.80Co_0.15Ti_0.05O₂

3D	1	3,3,3-	1.0	Nil	—	2180	709
	2	trifluoro-		Nb	0.5	2180	2105
	3	propyl-			1.0	2005	1990
	4	trimethoxy-		Mn	0.5	2178	2100
	5	silane			1.0	2002	1991
	6			Ti	0.5	2179	2105
	7				1.0	2005	1990
	8			Mg	0.5	2178	2105
	9				1.0	2000	1995
	10			Zr	0.5	2177	2100
	11				1.0	2000	1995
	12			Al	0.5	2179	2100
	13				1.0	2005	1992
	14			Mo	0.5	2178	2103
	15				1.0	2005	1995
	16			W	0.5	2177	2103
	17				1.0	2002	1990
	18			Y	0.5	2177	2103
	19				1.0	2002	1990
	21		2.5	Nil	—	1900	701
	22			Nb	0.5	1902	1800
	23				1.0	1804	1717
	24			Mn	0.5	1900	1802
	25				1.0	1800	1715
	26			Ti	0.5	1900	1804
	27				1.0	1802	1712
	28			Mg	0.5	1905	1805
	29				1.0	1800	1714
	30			Zr	0.5	1905	1800
	31				1.0	1804	1713
	32			Al	0.5	1904	1802
	33				1.0	1804	1713
	34			Mo	0.5	1904	1805
	35				1.0	1805	1717
	36			W	0.5	1900	1805
	37				1.0	1805	1717
	38			Y	0.5	1905	1805
	39				1.0	1804	1717

Batteries 3E-1 to 3E-39

Batteries 3E-1 to 3E-39 were fabricated in the same manner as in Batteries 3A-1 to 3A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3,3,4,4,5,5,6,6,6-nonafluorohexyltrichlorosilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 3E.

TABLE 3E

Lithium composite oxide: LiNi_0.80Co_0.15Ti_0.05O₂

			Intermittent cycle
			characteristics
			Capacity after
			500 cycles
		Element	Charge rest

Coupling agent

Le

720 min

	Adding	Adding	30 min	at
Battery	amount	amount	at 45° C.	45° C.
No.	(wt %)	(mol %)	(mAh)	(mAh)

3E	1	3,3,4,4,5,5,6,6,6-	1.0	Nil	—	2190	817
	2	nonafluoro-		Nb	0.5	2185	2105
	3	hexyl-			1.0	2008	1998
	4	trichloro-		Mn	0.5	2184	2105
	5	silane			1.0	2004	1997
	6			Ti	0.5	2184	2104
	7				1.0	2004	1999
	8			Mg	0.5	2185	2105
	9				1.0	2005	1997
	10			Zr	0.5	2187	2107
	11				1.0	2007	1998
	12			Al	0.5	2187	2107
	13				1.0	2008	1997
	14			Mo	0.5	2188	2108
	15				1.0	2004	1998
	16			W	0.5	2188	2108
	17				1.0	2005	1999
	18			Y	0.5	2187	2108
	19				1.0	2007	1999
	21		2.5	Nil	—	1910	704
	22			Nb	0.5	1910	1808
	23				1.0	1812	1705
	24			Mn	0.5	1908	1807
	25				1.0	1810	1704
	26			Ti	0.5	1907	1807
	27				1.0	1815	1700
	28			Mg	0.5	1908	1805
	29				1.0	1814	1702
	30			Zr	0.5	1909	1807
	31				1.0	1812	1705
	32			Al	0.5	1907	1809
	33				1.0	1810	1704
	34			Mo	0.5	1908	1807
	35				1.0	1815	1705
	36			W	0.5	1909	1808
	37				1.0	1814	1705
	38			Y	0.5	1912	1808
	39				1.0	1815	1704

Batteries 3F-1 to 3F-39

Batteries 3F-1 to 3F-39 were fabricated in the same manner as in Batteries 3A-1 to 3A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 6-triethoxysilyl-2-norbornene, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 3F.

TABLE 3F

Lithium composite oxide: LiNi_0.80Co_0.15Ti_0.05O₂

3F	1	6-triethoxy-	1.0	Nil	—	2190	822
	2	silyl-2-		Nb	0.5	2185	2105
	3	norbornene			1.0	2008	1998
	4			Mn	0.5	2184	2105
	5				1.0	2004	1997
	6			Ti	0.5	2184	2104
	7				1.0	2004	1999
	8			Mg	0.5	2185	2105
	9				1.0	2005	1997
	10			Zr	0.5	2187	2107
	11				1.0	2007	1998
	12			Al	0.5	2187	2107
	13				1.0	2008	1997
	14			Mo	0.5	2188	2108
	15				1.0	2004	1998
	16			W	0.5	2188	2108
	17				1.0	2005	1999
	18			Y	0.5	2187	2108
	19				1.0	2007	1999
	21		2.5	Nil	—	1911	702
	22			Nb	0.5	1910	1808
	23				1.0	1812	1705
	24			Mn	0.5	1908	1807
	25				1.0	1810	1704
	26			Ti	0.5	1907	1807
	27				1.0	1815	1700
	28			Mg	0.5	1908	1805
	29				1.0	1814	1702
	30			Zr	0.5	1909	1807
	31				1.0	1812	1705
	32			Al	0.5	1907	1809
	33				1.0	1810	1704
	34			Mo	0.5	1908	1807
	35				1.0	1815	1705
	36			W	0.5	1909	1808
	37				1.0	1814	1705
	38			Y	0.5	1912	1808
	39				1.0	1815	1704

Batteries 3R-1 to 3R-19

As Comparative Example, Batteries 3R-1 to 3R-19 were fabricated in the same manner as in Batteries 3A-1 to 3A-19, respectively, except that the silane coupling agent was not used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 3R.

TABLE 3R

Lithium composite oxide: LiNi_0.80Co_0.15Ti_0.05O₂

3R	1	Nil	—	Nil	—	2190	897
	2			Nb	0.5	2184	900
	3				1.0	2000	810
	4			Mn	0.5	2187	905
	5				1.0	2002	815
	6			Ti	0.5	2187	904
	7				1.0	2003	812
	8			Mg	0.5	2180	904
	9				1.0	2003	815
	10			Zr	0.5	2180	907
	11				1.0	2004	814
	12			Al	0.5	2188	900
	13				1.0	2002	814
	14			Mo	0.5	2188	907
	15				1.0	2002	810
	16			W	0.5	2187	907
	17				1.0	2002	813
	18			Y	0.5	2187	900
	19				1.0	2002	812

EXAMPLE 4

Batteries 4A-1 to 4A-39

Nickel sulfate, cobalt sulfate and titanium nitrate were mixed so that the molar ratio of Ni atom, Co atom and Ti atom was 34:33:33. To 10 L of water, 3.2 kg of the mixture thus obtained was dissolved to prepare a starting material solution. To the starting material solution, 400 g of sodium hydroxide was added to form a precipitate. The precipitate was washed with water sufficiently, and then dried to yield a coprecipitated hydroxide.
To 3 kg of the Ni—Co—Ti coprecipitated hydroxide thus obtained, 784 g of lithium hydroxide was added and mixed, and then the mixture was baked for 10 hours at a synthesizing temperature of 750° C. in an atmosphere with an oxygen partial pressure of 0.5 atm. As a result, a Ni/Co based Li composite oxide containing Ti as element L (LiNi_0.34CO_0.33Ti_0.33O₂) was obtained.
Batteries 4A-1 to 4A-39 were fabricated using 3-mercaptopropyltrimethoxysilane in the same manner as in Batteries 1A-1 to 1A-39 of Example 1, respectively, except that the Ni/Co based Li composite oxide thus obtained was used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 4A.

TABLE 4A

Lithium composite oxide: LiNi_0.34Co_0.33Ti_0.33O₂

4A	1	3-mercapto-	1.0	Nil	—	1912	787
	2	propyl-		Nb	0.5	1910	1862
	3	trimethoxy-			1.0	1825	1779
	4	silane		Mn	0.5	1915	1867
	5				1.0	1824	1778
	6			Ti	0.5	1911	1863
	7				1.0	1827	1781
	8			Mg	0.5	1915	1867
	9				1.0	1825	1770
	10			Zr	0.5	1917	1859
	11				1.0	1829	1774
	12			Al	0.5	1915	1858
	13				1.0	1824	1769
	14			Mo	0.5	1915	1858
	15				1.0	1828	1773
	16			W	0.5	1918	1860
	17				1.0	1827	1772
	18			Y	0.5	1911	1854
	19				1.0	1825	1770
	21		2.5	Nil	—	1915	751
	22			Nb	0.5	1918	1880
	23				1.0	1829	1792
	24			Mn	0.5	1912	1874
	25				1.0	1827	1790
	26			Ti	0.5	1915	1877
	27				1.0	1826	1789
	28			Mg	0.5	1911	1873
	29				1.0	1827	1790
	30			Zr	0.5	1914	1876
	31				1.0	1825	1789
	32			Al	0.5	1915	1877
	33				1.0	1827	1772
	34			Mo	0.5	1914	1857
	35				1.0	1829	1774
	36			W	0.5	1910	1853
	37				1.0	1827	1772
	38			Y	0.5	1912	1855
	39				1.0	1825	1770

Batteries 4B-1 to 4B-39

Batteries 4B-1 to 4B-39 were fabricated in the same manner as in Batteries 4A-1 to 4A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to hexyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 4B.

TABLE 4B

Lithium composite oxide: LiNi_0.34Co_0.33Ti_0.33O₂

4B	1	Hexyl-	1.0	Nil	—	1905	800
	2	trimethoxy-		Nb	0.5	1910	1872
	3	silane			1.0	1830	1793
	4			Mn	0.5	1908	1870
	5				1.0	1835	1798
	6			Ti	0.5	1907	1850
	7				1.0	1834	1779
	8			Mg	0.5	1908	1851
	9				1.0	1835	1780
	10			Zr	0.5	1905	1857
	11				1.0	1834	1788
	12			Al	0.5	1907	1859
	13				1.0	1836	1790
	14			Mo	0.5	1911	1863
	15				1.0	1837	1791
	16			W	0.5	1909	1871
	17				1.0	1839	1802
	18			Y	0.5	1912	1874
	19				1.0	1838	1801
	21		2.5	Nil	—	1910	754
	22			Nb	0.5	1915	1877
	23				1.0	1830	1793
	24			Mn	0.5	1918	1880
	25				1.0	1832	1795
	26			Ti	0.5	1912	1874
	27				1.0	1831	1794
	28			Mg	0.5	1914	1876
	29				1.0	1834	1797
	30			Zr	0.5	1914	1876
	31				1.0	1834	1797
	32			Al	0.5	1915	1877
	33				1.0	1835	1780
	34			Mo	0.5	1911	1854
	35				1.0	1830	1775
	36			W	0.5	1910	1853
	37				1.0	1832	1777
	38			Y	0.5	1912	1855
	39				1.0	1833	1778

Batteries 4C-1 to 4C-39

Batteries 4C-1 to 4C-39 were fabricated in the same manner as in Batteries 4A-1 to 4A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3-methacryloxypropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 4C.

TABLE 4C

Lithium composite oxide: LiNi_0.34Co_0.33Ti_0.33O₂

4C	1	3-methacry-	1.0	Nil	—	1920	892
	2	loxypropyl-		Nb	0.5	1915	1877
	3	trimethoxy-			1.0	1835	1798
	4	silane		Mn	0.5	1917	1879
	5				1.0	1834	1752
	6			Ti	0.5	1918	1833
	7				1.0	1837	1755
	8			Mg	0.5	1914	1829
	9				1.0	1835	1753
	10			Zr	0.5	1911	1854
	11				1.0	1837	1782
	12			Al	0.5	1915	1858
	13				1.0	1839	1784
	14			Mo	0.5	1912	1855
	15				1.0	1834	1779
	16			W	0.5	1917	1859
	17				1.0	1833	1778
	18			Y	0.5	1917	1859
	19				1.0	1830	1775
	21		2.5	Nil	—	1915	800
	22			Nb	0.5	1914	1829
	23				1.0	1837	1755
	24			Mn	0.5	1912	1827
	25				1.0	1834	1752
	26			Ti	0.5	1911	1873
	27				1.0	1830	1793
	28			Mg	0.5	1910	1872
	29				1.0	1831	1794
	30			Zr	0.5	1915	1858
	31				1.0	1832	1777
	32			Al	0.5	1914	1857
	33				1.0	1834	1779
	34			Mo	0.5	1912	1827
	35				1.0	1834	1752
	36			W	0.5	1911	1826
	37				1.0	1833	1796
	38			Y	0.5	1910	1872
	39				1.0	1830	1793

Batteries 4R-1 to 4R-19

As Comparative Example, Batteries 4R-1 to 4R-19 were fabricated in the same manner as in Batteries 4A-1 to 4A-19, respectively, except that the silane coupling agent was not used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 4R.

TABLE 4R

Lithium composite oxide: LiNi_0.34Co_0.33Ti_0.33O₂

4R	1	Nil	—	Nil	—	1920	725
	2			Nb	0.5	1912	754
	3				1.0	1842	702
	4			Mn	0.5	1910	754
	5				1.0	1840	701
	6			Ti	0.5	1911	755
	7				1.0	1840	700
	8			Mg	0.5	1914	752
	9				1.0	1840	704
	10			Zr	0.5	1915	751
	11				1.0	1840	704
	12			Al	0.5	1918	758
	13				1.0	1847	702
	14			Mo	0.5	1910	754
	15				1.0	1844	701
	16			W	0.5	1911	752
	17				1.0	1842	705
	18			Y	0.5	1912	755
	19				1.0	1843	700

EXAMPLE 5

Batteries 5A-1 to 5A-39

Nickel sulfate, cobalt sulfate and manganese sulfate were mixed so that the molar ratio of Ni atom, Co atom and Mn atom was 34:33:33. To 10 L of water, 3.2 kg of the mixture thus obtained was dissolved to prepare a starting material solution. To the starting material solution, 400 g of sodium hydroxide was added to form a precipitate. The precipitate was washed with water sufficiently, and then dried to yield a coprecipitated hydroxide.
To 3 kg of the Ni—Co—Mn coprecipitated hydroxide thus obtained, 784 g of lithium hydroxide was added and mixed, and then the mixture was baked for 10 hours at a synthesizing temperature of 750° C. in an atmosphere with an oxygen partial pressure of 0.5 atm. As a result, a Ni/Co based Li composite oxide containing Mn as element L (LiNi_0.34CO_0.33Mn_0.33O₂) was obtained.
Batteries 5A-1 to 5A-39 were fabricated using 3-mercaptopropyltrimethoxysilane in the same manner as in Batteries 1A-1 to 1A-39 of Example 1, respectively, except that the Ni/Co based Li composite oxide thus obtained was used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 5A.

TABLE 5A

Lithium composite oxide: LiNi_0.34Co_0.33Mn_0.33O₂

5A	1	3-mercapto-	1.0	Nil	—	2007	789
	2	propyl-		Nb	0.5	2001	1903
	3	trimethoxy-			1.0	1865	1750
	4	silane		Mn	0.5	2002	1900
	5				1.0	1866	1748
	6			Ti	0.5	2005	1902
	7				1.0	1866	1749
	8			Mg	0.5	2004	1905
	9				1.0	1867	1745
	10			Zr	0.5	2007	1904
	11				1.0	1865	1744
	12			Al	0.5	2000	1900
	13				1.0	1860	1743
	14			Mo	0.5	2001	1905
	15				1.0	1862	1749
	16			W	0.5	2002	1907
	17				1.0	1865	1745
	18			Y	0.5	2005	1907
	19				1.0	1864	1748
	21		2.5	Nil	—	1770	720
	22			Nb	0.5	1748	1698
	23				1.0	1645	1599
	24			Mn	0.5	1747	1690
	25				1.0	1648	1598
	26			Ti	0.5	1749	1692
	27				1.0	1644	1597
	28			Mg	0.5	1745	1692
	29				1.0	1642	1599
	30			Zr	0.5	1744	1695
	31				1.0	1645	1598
	32			Al	0.5	1740	1697
	33				1.0	1640	1597
	34			Mo	0.5	1748	1699
	35				1.0	1642	1595
	36			W	0.5	1749	1698
	37				1.0	1643	1599
	38			Y	0.5	1750	1695
	39				1.0	1645	1595

Batteries 5B-1 to 5B-39

Batteries 5B-1 to 5B-39 were fabricated in the same manner as in Batteries 5A-1 to 5A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to hexyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 5B.

TABLE 5B

Lithium composite oxide: LiNi_0.34Co_0.33Mn_0.33O₂

5B	1	Hexyl-	1.0	Nil	—	2007	804
	2	trimethoxy-		Nb	0.5	2005	1905
	3	silane			1.0	1842	1755
	4			Mn	0.5	2002	1907
	5				1.0	1840	1757
	6			Ti	0.5	2004	1905
	7				1.0	1845	1754
	8			Mg	0.5	2002	1904
	9				1.0	1844	1748
	10			Zr	0.5	2000	1905
	11				1.0	1845	1749
	12			Al	0.5	2001	1905
	13				1.0	1841	1757
	14			Mo	0.5	2002	1904
	15				1.0	1847	1755
	16			W	0.5	2005	1904
	17				1.0	1845	1757
	18			Y	0.5	2004	1907
	19				1.0	1847	1547
	21		2.5	Nil	—	1750	702
	22			Nb	0.5	1749	1607
	23				1.0	1645	1605
	24			Mn	0.5	1747	1704
	25				1.0	1646	1600
	26			Ti	0.5	1745	1704
	27				1.0	1647	1605
	28			Mg	0.5	1748	1707
	29				1.0	1644	1602
	30			Zr	0.5	1744	1705
	31				1.0	1645	1604
	32			Al	0.5	1740	1706
	33				1.0	1647	1608
	34			Mo	0.5	1743	1707
	35				1.0	1647	1608
	36			W	0.5	1744	1705
	37				1.0	1650	1607
	38			Y	0.5	1745	1701
	39				1.0	1650	1602

Batteries 5C-1 to 5C-39

Batteries 5C-1 to 5C-39 were fabricated in the same manner as in Batteries 5A-1 to 5A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3-methacryloxypropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 5C.

TABLE 5C

Lithium composite oxide: LiNi_0.34Co_0.33Mn_0.33O₂

5C	1	3-methacry-	1.0	Nil	—	2007	797
	2	loxypropyl-		Nb	0.5	2005	1910
	3	trimethoxy-			1.0	1860	1755
	4	silane		Mn	0.5	2002	1905
	5				1.0	1866	1757
	6			Ti	0.5	2005	1908
	7				1.0	1867	1750
	8			Mg	0.5	2000	1907
	9				1.0	1866	1752
	10			Zr	0.5	2002	1907
	11				1.0	1870	1753
	12			Al	0.5	2005	1907
	13				1.0	1872	1755
	14			Mo	0.5	2004	1908
	15				1.0	1870	1757
	16			W	0.5	2003	1909
	17				1.0	1869	1755
	18			Y	0.5	2003	1909
	19				1.0	1867	1757
	21		2.5	Nil	—	1755	707
	22			Nb	0.5	1750	1701
	23				1.0	1657	1607
	24			Mn	0.5	1755	1702
	25				1.0	1655	1607
	26			Ti	0.5	1757	1705
	27				1.0	1655	1607
	28			Mg	0.5	1747	1704
	29				1.0	1658	1605
	30			Zr	0.5	1748	1707
	31				1.0	1655	1600
	32			Al	0.5	1757	1705
	33				1.0	1660	1602
	34			Mo	0.5	1755	1707
	35				1.0	1667	1605
	36			W	0.5	1757	1705
	37				1.0	1664	1602
	38			Y	0.5	1755	1704
	39				1.0	1660	1605

Batteries 5D-1 to 5D-39

Batteries 5D-1 to 5D-39 were fabricated in the same manner as in Batteries 5A-1 to 5A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3,3,3-trifluoropropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 5D.

TABLE 5D

Lithium composite oxide: LiNi_0.34Co_0.33Mn_0.33O₂

5D	1	3,3,3-	1.0	Nil	—	2005	790
	2	trifluoro-		Nb	0.5	2004	1905
	3	propyl-			1.0	1855	1750
	4	trimethoxy-		Mn	0.5	2003	1900
	5	silane			1.0	1856	1749
	6			Ti	0.5	2002	1902
	7				1.0	1857	1748
	8			Mg	0.5	2000	1905
	9				1.0	1857	1744
	10			Zr	0.5	2004	1900
	11				1.0	1855	1744
	12			Al	0.5	2004	1904
	13				1.0	1850	1749
	14			Mo	0.5	2005	1905
	15				1.0	1854	1748
	16			W	0.5	2005	1905
	17				1.0	1850	1747
	18			Y	0.5	2004	1904
	19				1.0	1852	1747
	21		2.5	Nil	—	1750	722
	22			Nb	0.5	1740	1685
	23				1.0	1620	1600
	24			Mn	0.5	1745	1685
	25				1.0	1625	1600
	26			Ti	0.5	1740	1687
	27				1.0	1622	1602
	28			Mg	0.5	1744	1687
	29				1.0	1623	1605
	30			Zr	0.5	1743	1684
	31				1.0	1624	1604
	32			Al	0.5	1744	1689
	33				1.0	1625	1604
	34			Mo	0.5	1745	1684
	35				1.0	1625	1605
	36			W	0.5	1742	1685
	37				1.0	1625	1605
	38			Y	0.5	1744	1685
	39				1.0	1624	1605

Batteries 5E-1 to 5E-39

Batteries 5E-1 to 5E-39 were fabricated in the same manner as in Batteries 5A-1 to 5A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3,3,4,4,5,5,6,6,6-nonafluorohexyltrichlorosilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 5E.

TABLE 5E

Lithium composite oxide: LiNi_0.34Co_0.33Mn_0.33O₂

5E	1	3,3,4,4,5,5,	1.0	Nil	—	2002	871
	2	6,6,6-		Nb	0.5	1999	1898
	3	nonafluoro-			1.0	1847	1750
	4	hexyl-		Mn	0.5	1997	1899
	5	trichloro-			1.0	1845	1748
	6	silane		Ti	0.5	1999	1900
	7				1.0	1844	1749
	8			Mg	0.5	2000	1902
	9				1.0	1844	1745
	10			Zr	0.5	2000	1905
	11				1.0	1845	1748
	12			Al	0.5	1999	1899
	13				1.0	1846	1746
	14			Mo	0.5	1998	1898
	15				1.0	1847	1748
	16			W	0.5	1997	1897
	17				1.0	1848	1747
	18			Y	0.5	1997	1895
	19				1.0	1849	1747
	21		2.5	Nil	—	1750	701
	22			Nb	0.5	1745	1700
	23				1.0	1600	1600
	24			Mn	0.5	1748	1700
	25				1.0	1600	1607
	26			Ti	0.5	1749	1703
	27				1.0	1605	1605
	28			Mg	0.5	1748	1704
	29				1.0	1608	1607
	30			Zr	0.5	1744	1703
	31				1.0	1607	1601
	32			Al	0.5	1745	1705
	33				1.0	1605	1605
	34			Mo	0.5	1747	1706
	35				1.0	1607	1607
	36			W	0.5	1747	1707
	37				1.0	1606	1601
	38			Y	0.5	1751	1701
	39				1.0	1605	1604

Batteries 5F-1 to 5F-39

Batteries 5F-1 to 5F-39 were fabricated in the same manner as in Batteries 5A-1 to 5A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 6-triethoxysilyl-2-norbornene, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 5F.

TABLE 5F

Lithium composite oxide: LiNi_0.34Co_0.33Mn_0.33O₂

5F	1	6-triethoxy-	1.0	N il	—	2007	897
	2	silyl-2-		Nb	0.5	2000	1900
	3	norbornene			1.0	1850	1752
	4			Mn	0.5	2002	1905
	5				1.0	1840	1750
	6			Ti	0.5	2005	1900
	7				1.0	1845	1755
	8			Mg	0.5	2000	1905
	9				1.0	1847	1750
	10			Zr	0.5	2005	1905
	11				1.0	1847	1752
	12			Al	0.5	2000	1907
	13				1.0	1845	1752
	14			Mo	0.5	2001	1907
	15				1.0	1847	1750
	16			W	0.5	2003	1902
	17				1.0	1847	1750
	18			Y	0.5	2002	1902
	19				1.0	1847	1755
	21		2.5	Nil	—	1755	701
	22			Nb	0.5	1750	1700
	23				1.0	1650	1600
	24			Mn	0.5	1751	1702
	25				1.0	1648	1605
	26			Ti	0.5	1752	1705
	27				1.0	1649	1608
	28			Mg	0.5	1750	1705
	29				1.0	1647	1607
	30			Zr	0.5	1752	1700
	31				1.0	1648	1607
	32			Al	0.5	1751	1705
	33				1.0	1648	1604
	34			Mo	0.5	1750	1705
	35				1.0	1648	1604
	36			W	0.5	1749	1700
	37				1.0	1648	1606
	38			Y	0.5	1748	1700
	39				1.0	1650	1605

Batteries 5R-1 to 5R-19

As Comparative Example, Batteries 5R-1 to 5R-19 were fabricated in the same manner as in Batteries 5A-1 to 5A-19, respectively, except that the silane coupling agent was not used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 5R.

TABLE 5R

Lithium composite oxide: LiNi_0.34Co_0.33Mn_0.33O₂

5R	1	Nil	—	Nil	—	2010	809
	2			Nb	0.5	2002	802
	3				1.0	1866	801
	4			Mn	0.5	2005	799
	5				1.0	1867	805
	6			Ti	0.5	2000	804
	7				1.0	1866	802
	8			Mg	0.5	2005	804
	9				1.0	1869	806
	10			Zr	0.5	2005	802
	11				1.0	1870	799
	12			Al	0.5	2007	798
	13				1.0	1872	797
	14			Mo	0.5	2010	804
	15				1.0	1871	805
	16			W	0.5	2008	807
	17				1.0	1870	797
	18			Y	0.5	2009	799
	19				1.0	1867	797

EXAMPLE 6

Batteries 6A-1 to 6A-39

Nickel sulfate, cobalt sulfate and manganese sulfate were mixed so that the molar ratio of Ni atom, Co atom and Mn atom was 80:15:5. To 10 L of water, 3.2 kg of the mixture thus obtained was dissolved to prepare a starting material solution. To the starting material solution, 400 g of sodium hydroxide was added to form a precipitate. The precipitate was washed with water sufficiently, and then dried to yield a coprecipitated hydroxide.
To 3 kg of the Ni—Co—Mn coprecipitated hydroxide thus obtained, 784 g of lithium hydroxide was added and mixed, and then the mixture was baked for 10 hours at a synthesizing temperature of 750° C. in an atmosphere with an oxygen partial pressure of 0.5 atm. As a result, a Ni/Co based Li composite oxide containing Mn as element L (LiNi_0.80Cu_0.15Mn_0.05O₂) was obtained.
Batteries 6A-1 to 6A-39 were fabricated using 3-mercaptopropyltrimethoxysilane in the same manner as in Batteries 1A-1 to 1A-39 of Example 1, respectively, except that the Ni/Co based Li composite oxide thus obtained was used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 6A.

TABLE 6A

Lithium composite oxide: LiNi_0.80Co_0.15Mn_0.05O₂

6A	1	3-mercapto-	1.0	Nil	—	1770	717
	2	propyl-		Nb	0.5	1754	1719
	3	trimethoxy-			1.0	1721	1687
	4	silane		Mn	0.5	1752	1717
	5				1.0	1724	1690
	6			Ti	0.5	1750	1715
	7				1.0	1725	1691
	8			Mg	0.5	1748	1713
	9				1.0	1720	1686
	10			Zr	0.5	1749	1697
	11				1.0	1721	1669
	12			Al	0.5	1744	1692
	13				1.0	1722	1670
	14			Mo	0.5	1748	1696
	15				1.0	1728	1676
	16			W	0.5	1749	1697
	17				1.0	1729	1677
	18			Y	0.5	1745	1693
	19				1.0	1724	1672
	21		2.5	Nil	—	1735	697
	22			Nb	0.5	1722	1670
	23				1.0	1705	1662
	24			Mn	0.5	1724	1681
	25				1.0	1710	1667
	26			Ti	0.5	1728	1685
	27				1.0	1708	1665
	28			Mg	0.5	1724	1681
	29				1.0	1709	1658
	30			Zr	0.5	1726	1674
	31				1.0	1701	1650
	32			Al	0.5	1725	1673
	33				1.0	1705	1654
	34			Mo	0.5	1724	1672
	35				1.0	1707	1656
	36			W	0.5	1722	1670
	37				1.0	1709	1658
	38			Y	0.5	1721	1669
	39				1.0	1708	1657

Batteries 6B-1 to 6B-39

Batteries 6B-1 to 6B-39 were fabricated in the same manner as in Batteries 6A-1 to 6A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to hexyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 6B.

TABLE 6B

Lithium composite oxide: LiNi_0.80Co_0.15Mn_0.05O₂

6B	1	Hexyl-	1.0	Nil	—	1760	711
	2	trimethoxy-		Nb	0.5	1755	1711
	3	silane			1.0	1720	1677
	4			Mn	0.5	1751	1707
	5				1.0	1721	1678
	6			Ti	0.5	1752	1708
	7				1.0	1725	1682
	8			Mg	0.5	1755	1711
	9				1.0	1720	1677
	10			Zr	0.5	1754	1710
	11				1.0	1724	1681
	12			Al	0.5	1750	1706
	13				1.0	1725	1682
	14			Mo	0.5	1752	1708
	15				1.0	1720	1668
	16			W	0.5	1754	1701
	17				1.0	1721	1669
	18			Y	0.5	1752	1699
	19				1.0	1724	1672
	21		2.5	Nil	—	1751	671
	22			Nb	0.5	1729	1677
	23				1.0	1705	1671
	24			Mn	0.5	1747	1712
	25				1.0	1704	1670
	26			Ti	0.5	1745	1710
	27				1.0	1702	1668
	28			Mg	0.5	1748	1713
	29				1.0	1705	1671
	30			Zr	0.5	1744	1709
	31				1.0	1704	1653
	32			Al	0.5	1740	1688
	33				1.0	1702	1651
	34			Mo	0.5	1743	1691
	35				1.0	1701	1650
	36			W	0.5	1744	1692
	37				1.0	1709	1658
	38			Y	0.5	1745	1693
	39				1.0	1701	1650

Batteries 6C-1 to 6C-39

Batteries 6C-1 to 6C-39 were fabricated in the same manner as in Batteries 6A-1 to 6A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3-methacryloxypropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 6C.

TABLE 6C

Lithium composite oxide: LiNi_0.80Co_0.15Mn_0.05O₂

6C	1	3-	1.0	Nil	—	1760	697
	2	methacryloxy-		Nb	0.5	1752	1699
	3	propyl-			1.0	1722	1670
	4	trimethoxy-		Mn	0.5	1751	1698
	5	silane			1.0	1724	1672
	6			Ti	0.5	1755	1702
	7				1.0	1724	1672
	8			Mg	0.5	1752	1699
	9				1.0	1722	1670
	10			Zr	0.5	1755	1702
	11				1.0	1724	1672
	12			Al	0.5	1754	1701
	13				1.0	1727	1684
	14			Mo	0.5	1758	1714
	15				1.0	1722	1679
	16			W	0.5	1752	1708
	17				1.0	1724	1681
	18			Y	0.5	1757	1713
	19				1.0	1723	1680
	21		2.5	Nil	—	1720	677
	22			Nb	0.5	1722	1679
	23				1.0	1702	1659
	24			Mn	0.5	1724	1681
	25				1.0	1705	1662
	26			Ti	0.5	1728	1693
	27				1.0	1704	1670
	28			Mg	0.5	1725	1691
	29				1.0	1707	1673
	30			Zr	0.5	1724	1690
	31				1.0	1706	1672
	32			Al	0.5	1722	1688
	33				1.0	1708	1674
	34			Mo	0.5	1726	1691
	35				1.0	1704	1670
	36			W	0.5	1725	1691
	37				1.0	1705	1671
	38			Y	0.5	1727	1692
	39				1.0	1702	1668

Batteries 6R-1 to 6R-19

As Comparative Example, Batteries 6R-1 to 6R-19 were fabricated in the same manner as in Batteries 6A-1 to 6A-19, respectively, except that the silane coupling agent was not used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 6R.

TABLE 6R

Lithium composite oxide: LiNi_0.80Co_0.15Mn_0.05O₂

6R	1	Nil	—	Nil	—	1750	570
	2			Nb	0.5	1752	581
	3				1.0	1720	540
	4			Mn	0.5	1754	582
	5				1.0	1725	542
	6			Ti	0.5	1752	585
	7				1.0	1720	541
	8			Mg	0.5	1754	584
	9				1.0	1721	547
	10			Zr	0.5	1750	584
	11				1.0	1724	543
	12			Al	0.5	1754	587
	13				1.0	1720	542
	14			Mo	0.5	1752	589
	15				1.0	1724	540
	16			W	0.5	1754	587
	17				1.0	1725	541
	18			Y	0.5	1754	586
	19				1.0	1728	548

EXAMPLE 7

Batteries 7A-1 to 7A-39

Nickel sulfate and cobalt sulfate were mixed so that the molar ratio of Ni atom and Co atom was 75:25. To 10 L of water, 3.2 kg of the mixture thus obtained was dissolved to prepare a starting material solution. To the starting material solution, 400 g of sodium hydroxide was added to form a precipitate. The precipitate was washed with water sufficiently, and then dried to yield a coprecipitated hydroxide.
To 3 kg of the Ni—Co coprecipitated hydroxide thus obtained, 784 g of lithium hydroxide was added and mixed, and then the mixture was baked for 10 hours at a synthesizing temperature of 750° C. in an atmosphere with an oxygen partial pressure of 0.5 atm. As a result, a Ni/Co based Li composite oxide not containing element L (LiNi_0.75Co_0.25O₂) was obtained.
Batteries 7A-1 to 7A-39 were fabricated using 3-mercaptopropyltrimethoxysilane in the same manner as in Batteries 1A-1 to 1A-39 of Example 1, respectively, except that the Ni/Co based Li composite oxide not containing element L thus obtained was used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 7A.

TABLE 7A

Lithium composite oxide: LiNi_0.75Co_0.25O₂

7A	1	3-mercapto-	1.0	Nil	—	2188	710
	2	propyl-		Nb	0.5	2188	2180
	3	trimethoxy-			1.0	2020	2008
	4	silane		Mn	0.5	2185	2182
	5				1.0	2022	2005
	6			Ti	0.5	2184	2187
	7				1.0	2025	2004
	8			Mg	0.5	2187	2185
	9				1.0	2027	2002
	10			Zr	0.5	2185	2181
	11				1.0	2027	2001
	12			Al	0.5	2184	2187
	13				1.0	2025	2002
	14			Mo	0.5	2182	2181
	15				1.0	2027	2005
	16			W	0.5	2180	2180
	17				1.0	2027	2002
	18			Y	0.5	2188	2187
	19				1.0	2021	2000
	21		2.5	Nil	—	2007	692
	22			Nb	0.5	2002	1920
	23				1.0	1907	1815
	24			Mn	0.5	2005	1922
	25				1.0	1905	1817
	26			Ti	0.5	2004	1921
	27				1.0	1902	1812
	28			Mg	0.5	2006	1925
	29				1.0	1900	1810
	30			Zr	0.5	2003	1927
	31				1.0	1905	1817
	32			Al	0.5	2002	1923
	33				1.0	1902	1815
	34			Mo	0.5	2007	1924
	35				1.0	1901	1812
	36			W	0.5	2001	1925
	37				1.0	1905	1817
	38			Y	0.5	2003	1927
	39				1.0	1904	1817

Batteries 7B-1 to 7B-39

Batteries 7B-1 to 7B-39 were fabricated in the same manner as in Batteries 7A-1 to 7A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to hexyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 7B.

TABLE 7B

Lithium composite oxide: LiNi_0.75Co_0.25O₂

7B	1	Hexyl-	1.0	Nil	—	2190	715
	2	trimethoxy-		Nb	0.5	2187	2155
	3	silane			1.0	2015	2004
	4			Mn	0.5	2185	2160
	5				1.0	2012	2002
	6			Ti	0.5	2184	2154
	7				1.0	2010	2000
	8			Mg	0.5	2182	2155
	9				1.0	2015	2001
	10			Zr	0.5	2188	2154
	11				1.0	2010	2002
	12			Al	0.5	2187	2157
	13				1.0	2012	2005
	14			Mo	0.5	2189	2155
	15				1.0	2012	2004
	16			W	0.5	2188	2158
	17				1.0	2010	2003
	18			Y	0.5	2185	2154
	19				1.0	2011	2003
	21		2.5	Nil	—	2000	620
	22			Nb	0.5	2002	1905
	23				1.0	1900	1801
	24			Mn	0.5	2005	1902
	25				1.0	1905	1802
	26			Ti	0.5	2007	1901
	27				1.0	1907	1805
	28			Mg	0.5	2005	1907
	29				1.0	1905	1804
	30			Zr	0.5	2007	1902
	31				1.0	1907	1804
	32			Al	0.5	2001	1905
	33				1.0	1904	1802
	34			Mo	0.5	2005	1907
	35				1.0	1902	1800
	36			W	0.5	2008	1905
	37				1.0	1904	1807
	38			Y	0.5	2001	1900
	39				1.0	1902	1807

Batteries 7C-1 to 7C-39

Batteries 7C-1 to 7C-39 were fabricated in the same manner as in Batteries 7A-1 to 7A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3-methacryloxypropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 7C.

TABLE 7C

Lithium composite oxide: LiNi_0.75Co_0.25O₂

7C	1	3-	1.0	Nil	—	2192	740
	2	methacryloxy-		Nb	0.5	2188	2145
	3	propyl-			1.0	2012	2004
	4	trimethoxy-		Mn	0.5	2180	2140
	5	silane			1.0	2017	2005
	6			Ti	0.5	2185	2144
	7				1.0	2012	2007
	8			Mg	0.5	2182	2142
	9				1.0	2010	2002
	10			Zr	0.5	2187	2147
	11				1.0	2017	2000
	12			Al	0.5	2187	2145
	13				1.0	2015	2007
	14			Mo	0.5	2185	2144
	15				1.0	2017	2005
	16			W	0.5	2181	2142
	17				1.0	2015	2002
	18			Y	0.5	2187	2147
	19				1.0	2011	2007
	21		2.5	Nil	—	2007	627
	22			Nb	0.5	2005	1910
	23				1.0	1908	1805
	24			Mn	0.5	2002	1908
	25				1.0	1905	1802
	26			Ti	0.5	2005	1907
	27				1.0	1907	1800
	28			Mg	0.5	2004	1911
	29				1.0	1901	1805
	30			Zr	0.5	2003	1907
	31				1.0	1905	1807
	32			Al	0.5	2004	1908
	33				1.0	1907	1807
	34			Mo	0.5	2005	1909
	35				1.0	1905	1805
	36			W	0.5	2002	1912
	37				1.0	1902	1800
	38			Y	0.5	2001	1911
	39				1.0	1904	1801

Batteries 7D-1 to 7D-39

Batteries 7D-1 to 7D-39 were fabricated in the same manner as in Batteries 7A-1 to 7A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3,3,3-trifluoropropyltrimethoxysilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 7D.

TABLE 7D

Lithium composite oxide: LiNi_0.75Co_0.25O ₂

7D	1	3,3,3-	1.0	Ni l	—	2187	725
	2	trifluoro-		Nb	0.5	2177	2100
	3	propyl-			1.0	2010	2005
	4	trimethoxy-		Mn	0.5	2175	2105
	5	silane			1.0	2011	2002
	6			Ti	0.5	2174	2104
	7				1.0	2009	2000
	8			Mg	0.5	2175	2103
	9				1.0	2012	2001
	10			Zr	0.5	2177	2102
	11				1.0	2011	2000
	12			Al	0.5	2171	2100
	13				1.0	2015	2005
	14			Mo	0.5	2172	2101
	15				1.0	2013	2004
	16			W	0.5	2172	2107
	17				1.0	2010	2002
	18			Y	0.5	2177	2107
	19				1.0	2008	2000
	21		2.5	Nil	—	2007	711
	22			Nb	0.5	2002	1908
	23				1.0	1905	1802
	24			Mn	0.5	2001	1902
	25				1.0	1904	1800
	26			Ti	0.5	2004	1905
	27				1.0	1902	1800
	28			Mg	0.5	2000	1904
	29				1.0	1900	1807
	30			Zr	0.5	2001	1905
	31				1.0	1907	1804
	32			Al	0.5	2005	1904
	33				1.0	1905	1805
	34			Mo	0.5	2001	1908
	35				1.0	1900	1802
	36			W	0.5	2004	1902
	37				1.0	1907	1804
	38			Y	0.5	2000	1900
	39				1.0	1905	1802

Batteries 7E-1 to 7E-39

Batteries 7E-1 to 7E-39 were fabricated in the same manner as in Batteries 7A-1 to 7A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 3,3,4,4,5,5,6,6,6-nonafluorohexyltrichlorosilane, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 7E.

TABLE 7E

Lithium composite oxide: LiNi_0.75Co_0.25O₂

7E	1	3,3,4,4,5,5,	1.0	Nil	—	2188	712
	2	6,6,6-		Nb	0.5	2180	2155
	3	nonafluoro-			1.0	2017	2004
	4	hexyl-		Mn	0.5	2182	2156
	5	trichloro-			1.0	2015	2007
	6	silane		Ti	0.5	2188	2155
	7				1.0	2012	2008
	8			Mg	0.5	2187	2157
	9				1.0	2011	2000
	10			Zr	0.5	2185	2154
	11				1.0	2011	2000
	12			Al	0.5	2184	2152
	13				1.0	2017	2002
	14			Mo	0.5	2185	2150
	15				1.0	2015	2003
	16			W	0.5	2187	2155
	17				1.0	2011	2007
	18			Y	0.5	2188	2157
	19				1.0	2014	2005
	21		2.5	Nil	—	2003	671
	22			Nb	0.5	2000	1902
	23				1.0	1900	1801
	24			Mn	0.5	2002	1901
	25				1.0	1902	1802
	26			Ti	0.5	2001	1902
	27				1.0	1901	1800
	28			Mg	0.5	2001	1905
	29				1.0	1905	1800
	30			Zr	0.5	2002	1908
	31				1.0	1904	1802
	32			Al	0.5	2004	1907
	33				1.0	1903	1810
	34			Mo	0.5	2003	1908
	35				1.0	1902	1809
	36			W	0.5	2002	1905
	37				1.0	1900	1807
	38			Y	0.5	2003	1904
	39				1.0	1900	1805

Batteries 7F-1 to 7F-39

Batteries 7F-1 to 7F-39 were fabricated in the same manner as in Batteries 7A-1 to 7A-39, respectively, except that the silane coupling agent to be added to the positive electrode material mixture paste was changed to 6-triethoxysilyl-2-norbornene, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 7F.

TABLE 7F

Lithium composite oxide: LiNi_0.75Co_0.25O₂

7F	1	6-triethoxy-	1.0	Nil	—	2187	717
	2	silyl-2-		Nb	0.5	2187	2150
	3	norbornene			1.0	2015	2000
	4			Mn	0.5	2188	2155
	5				1.0	2020	2002
	6			Ti	0.5	2189	2157
	7				1.0	2022	2005
	8			Mg	0.5	2187	2155
	9				1.0	2018	2004
	10			Zr	0.5	2185	2155
	11				1.0	2017	2005
	12			Al	0.5	2189	2150
	13				1.0	2020	2004
	14			Mo	0.5	2188	2152
	15				1.0	2019	2005
	16			W	0.5	2190	2154
	17				1.0	2017	2000
	18			Y	0.5	2192	2150
	19				1.0	2018	2000
	21		2.5	Nil	—	2002	657
	22			Nb	0.5	2005	1910
	23				1.0	1908	1805
	24			Mn	0.5	2004	1912
	25				1.0	1905	1802
	26			Ti	0.5	2000	1907
	27				1.0	1904	1800
	28			Mg	0.5	2005	1907
	29				1.0	1907	1805
	30			Zr	0.5	2007	1907
	31				1.0	1905	1807
	32			Al	0.5	2005	1905
	33				1.0	1907	1805
	34			Mo	0.5	2000	1907
	35				1.0	1908	1804
	36			W	0.5	2002	1910
	37				1.0	1909	1802
	38			Y	0.5	2003	1917
	39				1.0	1907	1809

Batteries 7R-1 to 7R-19

As Comparative Example, Batteries 7R-1 to 7R-19 were fabricated in the same manner as in Batteries 7A-1 to 7A-19, respectively, except that the silane coupling agent was not used, and the intermittent cycle characteristics thereof were evaluated in the same manner. The results are shown in Table 7R.

TABLE 7R

Lithium composite oxide: LiNi_0.75Co_0.25O₂

7R	1	Nil	—	Nil	—	2188	712
	2			Nb	0.5	2187	812
	3				1.0	2020	817
	4			Mn	0.5	2187	810
	5				1.0	2015	823
	6			Ti	0.5	2187	824
	7				1.0	2017	825
	8			Mg	0.5	2178	845
	9				1.0	2020	814
	10			Zr	0.5	2179	810
	11				1.0	2022	826
	12			Al	0.5	2175	825
	13				1.0	2025	822
	14			Mo	0.5	2180	823
	15				1.0	2027	822
	16			W	0.5	2182	820
	17				1.0	2021	825
	18			Y	0.5	2187	827
	19				1.0	2020	827

In the subsequent Examples, evaluations were performed with respect to lithium composite oxides synthesized using various starting materials in place of the above-described Ni/Co based Li composite oxides; however, the description of these is omitted.

INDUSTRIAL APPLICABILITY

The present invention is useful in a lithium ion secondary battery including, as a positive electrode active material, a lithium composite oxide mainly composed of nickel or cobalt. According to the present invention, the cycle characteristics under the conditions more similar to the conditions in practical use of lithium ion secondary batteries (for example, intermittent cycles) can be more improved than before without impairing the ability of suppressing gas generation or heat generation due to internal short-circuit.
The shape of the lithium ion secondary battery of the present invention is not particularly limited, and the battery may be of any shape, for example, a coin shape, a button shape, a sheet shape, a cylindrical shape, a flat shape, a rectangular shape and the like. As for the form of the electrode assembly comprising a positive electrode, a negative electrode and a separator, it may be a wound type or a stacked type. As for the size of the battery, it may be a small size for use in small portable devices etc. or a large size for use in electric cars etc. The lithium ion secondary battery of the present invention is applicable, for example, as a power supply for personal digital assistants, portable electronic devices, compact home electrical energy storage devices, motorcycles, electric cars, hybrid electric cars and the like. However, the applications thereof are not particularly limited.

Claims

1. A lithium ion secondary battery having a chargeable and dischargeable positive electrode, a chargeable and dischargeable negative electrode, and a non-aqueous electrolyte, wherein

said positive electrode includes active material particles,

said active material particles include a lithium composite oxide,

said lithium composite oxide is represented by the general formula (I): Li_xM_1-yL_yO₂O,

the general formula (I) satisfies 0.85≦x≦1.25 and 0≦y≦0.50,

element M is at least one selected from the group consisting of Ni and Co,

element L is at least one selected from the group consisting of alkaline earth elements, transition metal elements, rare earth elements, Group IIIb elements and Group IVb elements,

the surface layer of said active material particles includes element Le being at least one selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W and Y, and

said active material particles are surface-treated with a coupling agent.

2. The lithium ion secondary battery in accordance with claim 1, wherein in the general formula (I), 0<y, and element L includes at least one selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W and Y as an essential element.

3. The lithium ion secondary battery in accordance with claim 1, wherein element L and element Le form crystalline structures different from each other.

4. The lithium ion secondary battery in accordance with claim 1, wherein element Le forms an oxide having a crystalline structure different from that of said lithium composite oxide.

5. The lithium ion secondary battery in accordance with claim 1, wherein an amount of said coupling agent is less than or equal to 2 parts by weight relative to 100 parts by weight of said active material particles.

6. The lithium ion secondary battery in accordance with claim 1, wherein said coupling agent is a silane coupling agent.

7. The lithium ion secondary battery in accordance with claim 6, wherein said silane coupling agent includes at least one selected from the group consisting of an alkoxide group and a chlorine atom, and at least one selected from the group consisting of a mercapto group, an alkyl group and a fluorine atom.

8. The lithium ion secondary battery in accordance with claim 6, wherein said silane coupling agent forms a silicon compound bonded to the surface of said active material particles through Si—O bonds.

9. The lithium ion secondary battery in accordance with claim 1, wherein a mean particle size of said active material particles is more than or equal to 10 μm.

10. The lithium ion secondary battery in accordance with claim 1, wherein said non-aqueous electrolyte includes at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, phosphazene and fluorobenzene.